diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6decabdc3..274981073 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,8 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 - Support for Conditional Formatting Color Scale. [PR #3738](https://github.com/PHPOffice/PhpSpreadsheet/pull/3738)
 - Support Additional Tags in Helper/Html. [Issue #3751](https://github.com/PHPOffice/PhpSpreadsheet/issues/3751) [PR #3752](https://github.com/PHPOffice/PhpSpreadsheet/pull/3752)
 - Writer ODS : Write Border Style for cells [Issue #3690](https://github.com/PHPOffice/PhpSpreadsheet/issues/3690) [PR #3693](https://github.com/PHPOffice/PhpSpreadsheet/pull/3693)
+- Sheet Background Images [Issue #1649](https://github.com/PHPOffice/PhpSpreadsheet/issues/1649) [PR #3795](https://github.com/PHPOffice/PhpSpreadsheet/pull/3795)
+- Check if Coordinate is Inside Range [PR #3779](https://github.com/PHPOffice/PhpSpreadsheet/pull/3779)
 
 ### Changed
 
@@ -72,6 +74,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 - Theme File Missing but Referenced in Spreadsheet. [Issue #3770](https://github.com/PHPOffice/PhpSpreadsheet/issues/3770) [PR #3772](https://github.com/PHPOffice/PhpSpreadsheet/pull/3772)
 - Slk Shared Formulas. [Issue #2267](https://github.com/PHPOffice/PhpSpreadsheet/issues/2267) [PR #3776](https://github.com/PHPOffice/PhpSpreadsheet/pull/3776)
 - Html omitting some charts. [Issue #3767](https://github.com/PHPOffice/PhpSpreadsheet/issues/3767) [PR #3771](https://github.com/PHPOffice/PhpSpreadsheet/pull/3771)
+- Case Insensitive Comparison for Sheet Names [PR #3791](https://github.com/PHPOffice/PhpSpreadsheet/pull/3791)
 
 ## 1.29.0 - 2023-06-15
 
diff --git a/src/PhpSpreadsheet/Reader/Xlsx.php b/src/PhpSpreadsheet/Reader/Xlsx.php
index 99fb3937d..73ac43afd 100644
--- a/src/PhpSpreadsheet/Reader/Xlsx.php
+++ b/src/PhpSpreadsheet/Reader/Xlsx.php
@@ -973,6 +973,7 @@ class Xlsx extends BaseReader
 
                             if ($this->readDataOnly === false) {
                                 $this->readAutoFilter($xmlSheetNS, $docSheet);
+                                $this->readBackgroundImage($xmlSheetNS, $docSheet, dirname("$dir/$fileWorksheet") . '/_rels/' . basename($fileWorksheet) . '.rels');
                             }
 
                             $this->readTables($xmlSheetNS, $docSheet, $dir, $fileWorksheet, $zip, $mainNS);
@@ -2201,6 +2202,27 @@ class Xlsx extends BaseReader
         }
     }
 
+    private function readBackgroundImage(
+        SimpleXMLElement $xmlSheet,
+        Worksheet $docSheet,
+        string $relsName
+    ): void {
+        if ($xmlSheet && $xmlSheet->picture) {
+            $id = (string) self::getArrayItem(self::getAttributes($xmlSheet->picture, Namespaces::SCHEMA_OFFICE_DOCUMENT), 'id');
+            $rels = $this->loadZip($relsName);
+            foreach ($rels->Relationship as $rel) {
+                $attrs = $rel->attributes() ?? [];
+                $rid = (string) ($attrs['Id'] ?? '');
+                $target = (string) ($attrs['Target'] ?? '');
+                if ($rid === $id && substr($target, 0, 2) === '..') {
+                    $target = 'xl' . substr($target, 2);
+                    $content = $this->getFromZipArchive($this->zip, $target);
+                    $docSheet->setBackgroundImage($content);
+                }
+            }
+        }
+    }
+
     private function readTables(
         SimpleXMLElement $xmlSheet,
         Worksheet $docSheet,
diff --git a/src/PhpSpreadsheet/Worksheet/Worksheet.php b/src/PhpSpreadsheet/Worksheet/Worksheet.php
index 8ed1d22eb..89c545852 100644
--- a/src/PhpSpreadsheet/Worksheet/Worksheet.php
+++ b/src/PhpSpreadsheet/Worksheet/Worksheet.php
@@ -3879,4 +3879,47 @@ class Worksheet implements IComparable
 
         return $xfIndex;
     }
+
+    private string $backgroundImage = '';
+
+    private string $backgroundMime = '';
+
+    private string $backgroundExtension = '';
+
+    public function getBackgroundImage(): string
+    {
+        return $this->backgroundImage;
+    }
+
+    public function getBackgroundMime(): string
+    {
+        return $this->backgroundMime;
+    }
+
+    public function getBackgroundExtension(): string
+    {
+        return $this->backgroundExtension;
+    }
+
+    /**
+     * Set background image.
+     * Used on read/write for Xlsx.
+     * Used on write for Html.
+     *
+     * @param string $backgroundImage Image represented as a string, e.g. results of file_get_contents
+     */
+    public function setBackgroundImage(string $backgroundImage): self
+    {
+        $imageArray = getimagesizefromstring($backgroundImage) ?: ['mime' => ''];
+        $mime = $imageArray['mime'];
+        if ($mime !== '') {
+            $extension = explode('/', $mime);
+            $extension = $extension[1];
+            $this->backgroundImage = $backgroundImage;
+            $this->backgroundMime = $mime;
+            $this->backgroundExtension = $extension;
+        }
+
+        return $this;
+    }
 }
diff --git a/src/PhpSpreadsheet/Writer/Html.php b/src/PhpSpreadsheet/Writer/Html.php
index ecb99219d..b4547637c 100644
--- a/src/PhpSpreadsheet/Writer/Html.php
+++ b/src/PhpSpreadsheet/Writer/Html.php
@@ -878,6 +878,11 @@ class Html extends BaseWriter
             $css["table.sheet$sheetIndex"]['page-break-inside'] = 'avoid';
             $css["table.sheet$sheetIndex"]['break-inside'] = 'avoid';
         }
+        $picture = $sheet->getBackgroundImage();
+        if ($picture !== '') {
+            $base64 = base64_encode($picture);
+            $css["table.sheet$sheetIndex"]['background-image'] = 'url(data:' . $sheet->getBackgroundMime() . ';base64,' . $base64 . ')';
+        }
 
         // Build styles
         // Calculate column widths
diff --git a/src/PhpSpreadsheet/Writer/Xlsx.php b/src/PhpSpreadsheet/Writer/Xlsx.php
index c18bc8586..e127ccac9 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx.php
@@ -365,7 +365,7 @@ class Xlsx extends BaseWriter
         // Add worksheet relationships (drawings, ...)
         for ($i = 0; $i < $this->spreadSheet->getSheetCount(); ++$i) {
             // Add relationships
-            $zipContent['xl/worksheets/_rels/sheet' . ($i + 1) . '.xml.rels'] = $this->getWriterPartRels()->writeWorksheetRelationships($this->spreadSheet->getSheet($i), ($i + 1), $this->includeCharts, $tableRef1);
+            $zipContent['xl/worksheets/_rels/sheet' . ($i + 1) . '.xml.rels'] = $this->getWriterPartRels()->writeWorksheetRelationships($this->spreadSheet->getSheet($i), ($i + 1), $this->includeCharts, $tableRef1, $zipContent);
 
             // Add unparsedLoadedData
             $sheetCodeName = $this->spreadSheet->getSheet($i)->getCodeName();
diff --git a/src/PhpSpreadsheet/Writer/Xlsx/ContentTypes.php b/src/PhpSpreadsheet/Writer/Xlsx/ContentTypes.php
index 8faa3ffc2..3357e657f 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx/ContentTypes.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx/ContentTypes.php
@@ -186,6 +186,13 @@ class ContentTypes extends WriterPart
                     }
                 }
             }
+
+            $bgImage = $spreadsheet->getSheet($i)->getBackgroundImage();
+            $mimeType = $spreadsheet->getSheet($i)->getBackgroundMime();
+            $extension = $spreadsheet->getSheet($i)->getBackgroundExtension();
+            if ($bgImage !== '' && !isset($aMediaContentTypes[$mimeType])) {
+                $this->writeDefaultContentType($objWriter, $extension, $mimeType);
+            }
         }
 
         // unparsed defaults
diff --git a/src/PhpSpreadsheet/Writer/Xlsx/Rels.php b/src/PhpSpreadsheet/Writer/Xlsx/Rels.php
index 977dc9abf..dce5882ce 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx/Rels.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx/Rels.php
@@ -169,7 +169,7 @@ class Rels extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeWorksheetRelationships(\PhpOffice\PhpSpreadsheet\Worksheet\Worksheet $worksheet, $worksheetId = 1, $includeCharts = false, $tableRef = 1)
+    public function writeWorksheetRelationships(\PhpOffice\PhpSpreadsheet\Worksheet\Worksheet $worksheet, $worksheetId = 1, $includeCharts = false, $tableRef = 1, array &$zipContent = [])
     {
         // Create XML writer
         $objWriter = null;
@@ -221,6 +221,20 @@ class Rels extends WriterPart
             );
         }
 
+        $backgroundImage = $worksheet->getBackgroundImage();
+        if ($backgroundImage !== '') {
+            $rId = 'Bg';
+            $uniqueName = md5(mt_rand(0, 9999) . time() . mt_rand(0, 9999));
+            $relPath = "../media/$uniqueName." . $worksheet->getBackgroundExtension();
+            $this->writeRelationship(
+                $objWriter,
+                $rId,
+                Namespaces::IMAGE,
+                $relPath
+            );
+            $zipContent["xl/media/$uniqueName." . $worksheet->getBackgroundExtension()] = $backgroundImage;
+        }
+
         // Write hyperlink relationships?
         $i = 1;
         foreach ($worksheet->getHyperlinkCollection() as $hyperlink) {
diff --git a/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php b/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
index 7efaaf939..de9cc49e7 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php
@@ -139,6 +139,9 @@ class Worksheet extends WriterPart
         // IgnoredErrors
         $this->writeIgnoredErrors($objWriter);
 
+        // BackgroundImage must come after ignored, before table
+        $this->writeBackgroundImage($objWriter, $worksheet);
+
         // Table
         $this->writeTable($objWriter, $worksheet);
 
@@ -1042,6 +1045,9 @@ class Worksheet extends WriterPart
     private function writeTable(XMLWriter $objWriter, PhpspreadsheetWorksheet $worksheet): void
     {
         $tableCount = $worksheet->getTableCollection()->count();
+        if ($tableCount === 0) {
+            return;
+        }
 
         $objWriter->startElement('tableParts');
         $objWriter->writeAttribute('count', (string) $tableCount);
@@ -1055,6 +1061,18 @@ class Worksheet extends WriterPart
         $objWriter->endElement();
     }
 
+    /**
+     * Write Background Image.
+     */
+    private function writeBackgroundImage(XMLWriter $objWriter, PhpspreadsheetWorksheet $worksheet): void
+    {
+        if ($worksheet->getBackgroundImage() !== '') {
+            $objWriter->startElement('picture');
+            $objWriter->writeAttribute('r:id', 'rIdBg');
+            $objWriter->endElement();
+        }
+    }
+
     /**
      * Write PageSetup.
      */
@@ -1098,19 +1116,31 @@ class Worksheet extends WriterPart
     private function writeHeaderFooter(XMLWriter $objWriter, PhpspreadsheetWorksheet $worksheet): void
     {
         // headerFooter
+        $headerFooter = $worksheet->getHeaderFooter();
+        $oddHeader = $headerFooter->getOddHeader();
+        $oddFooter = $headerFooter->getOddFooter();
+        $evenHeader = $headerFooter->getEvenHeader();
+        $evenFooter = $headerFooter->getEvenFooter();
+        $firstHeader = $headerFooter->getFirstHeader();
+        $firstFooter = $headerFooter->getFirstFooter();
+        if ("$oddHeader$oddFooter$evenHeader$evenFooter$firstHeader$firstFooter" === '') {
+            return;
+        }
+
         $objWriter->startElement('headerFooter');
         $objWriter->writeAttribute('differentOddEven', ($worksheet->getHeaderFooter()->getDifferentOddEven() ? 'true' : 'false'));
         $objWriter->writeAttribute('differentFirst', ($worksheet->getHeaderFooter()->getDifferentFirst() ? 'true' : 'false'));
         $objWriter->writeAttribute('scaleWithDoc', ($worksheet->getHeaderFooter()->getScaleWithDocument() ? 'true' : 'false'));
         $objWriter->writeAttribute('alignWithMargins', ($worksheet->getHeaderFooter()->getAlignWithMargins() ? 'true' : 'false'));
 
-        $objWriter->writeElement('oddHeader', $worksheet->getHeaderFooter()->getOddHeader());
-        $objWriter->writeElement('oddFooter', $worksheet->getHeaderFooter()->getOddFooter());
-        $objWriter->writeElement('evenHeader', $worksheet->getHeaderFooter()->getEvenHeader());
-        $objWriter->writeElement('evenFooter', $worksheet->getHeaderFooter()->getEvenFooter());
-        $objWriter->writeElement('firstHeader', $worksheet->getHeaderFooter()->getFirstHeader());
-        $objWriter->writeElement('firstFooter', $worksheet->getHeaderFooter()->getFirstFooter());
-        $objWriter->endElement();
+        self::writeElementIf($objWriter, $oddHeader !== '', 'oddHeader', $oddHeader);
+        self::writeElementIf($objWriter, $oddFooter !== '', 'oddFooter', $oddFooter);
+        self::writeElementIf($objWriter, $evenHeader !== '', 'evenHeader', $evenHeader);
+        self::writeElementIf($objWriter, $evenFooter !== '', 'evenFooter', $evenFooter);
+        self::writeElementIf($objWriter, $firstHeader !== '', 'firstHeader', $firstHeader);
+        self::writeElementIf($objWriter, $firstFooter !== '', 'firstFooter', $firstFooter);
+
+        $objWriter->endElement(); // headerFooter
     }
 
     /**
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/BackgroundImageTest.php b/tests/PhpSpreadsheetTests/Writer/Html/BackgroundImageTest.php
new file mode 100644
index 000000000..df73c9cd8
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Writer/Html/BackgroundImageTest.php
@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
+
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheet\Writer\Html;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+
+class BackgroundImageTest extends AbstractFunctional
+{
+    public function testBackgroundImage(): void
+    {
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $sheet->getCell('A1')->setValue(1);
+        $sheet->getCell('B1')->setValue(2);
+        $sheet->getCell('A2')->setValue(3);
+        $sheet->getCell('B2')->setValue(4);
+        $imageFile = 'tests/data/Writer/XLSX/backgroundtest.png';
+        $image = (string) file_get_contents($imageFile);
+        $sheet->setBackgroundImage($image);
+        self::assertSame('image/png', $sheet->getBackgroundMime());
+        self::assertSame('png', $sheet->getBackgroundExtension());
+        $writer = new Html($spreadsheet);
+        $header = $writer->generateHTMLHeader(true);
+        self::assertStringContainsString('table.sheet0 { background-image:url(data:image/png;base64,', $header);
+        $spreadsheet->disconnectWorksheets();
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/BackgroundImageTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/BackgroundImageTest.php
new file mode 100644
index 000000000..73a32db3a
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/BackgroundImageTest.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
+
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+
+class BackgroundImageTest extends AbstractFunctional
+{
+    public function testBackgroundImage(): void
+    {
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $sheet->getCell('A1')->setValue(1);
+        $sheet->getCell('B1')->setValue(2);
+        $sheet->getCell('A2')->setValue(3);
+        $sheet->getCell('B2')->setValue(4);
+        $imageFile = 'tests/data/Writer/XLSX/backgroundtest.png';
+        $image = (string) file_get_contents($imageFile);
+        $sheet->setBackgroundImage($image);
+        self::assertSame('image/png', $sheet->getBackgroundMime());
+        self::assertSame('png', $sheet->getBackgroundExtension());
+
+        $reloadedSpreadsheet = $this->writeAndReload($spreadsheet, 'Xlsx');
+        $spreadsheet->disconnectWorksheets();
+        $reloadedWorksheet = $reloadedSpreadsheet->getActiveSheet();
+        self::assertSame($image, $reloadedWorksheet->getBackgroundImage());
+        self::assertSame('image/png', $reloadedWorksheet->getBackgroundMime());
+        self::assertSame('png', $reloadedWorksheet->getBackgroundExtension());
+        self::assertSame(2, $reloadedWorksheet->getCell('B1')->getValue());
+        $reloadedSpreadsheet->disconnectWorksheets();
+    }
+
+    public function testInvalidImage(): void
+    {
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $sheet->getCell('A1')->setValue(1);
+        $imageFile = __FILE__;
+        $image = (string) file_get_contents($imageFile);
+        self::assertNotSame('', $image);
+        $sheet->setBackgroundImage($image);
+        self::assertSame('', $sheet->getBackgroundImage());
+        self::assertSame('', $sheet->getBackgroundMime());
+        self::assertSame('', $sheet->getBackgroundExtension());
+        $spreadsheet->disconnectWorksheets();
+    }
+}
diff --git a/tests/data/Writer/XLSX/backgroundtest.png b/tests/data/Writer/XLSX/backgroundtest.png
new file mode 100644
index 000000000..3f14e4b3f
Binary files /dev/null and b/tests/data/Writer/XLSX/backgroundtest.png differ