Icons.php 

<?php

declare(strict_types=1);

use TYPO3\CMS\Core\Imaging\IconProvider\BitmapIconProvider;
use TYPO3\CMS\Core\Imaging\IconProvider\SvgIconProvider;
use TYPO3\CMS\Core\Imaging\IconProvider\SvgSpriteIconProvider;

return [
  // Icon identifier
  'tx-myextension-svgicon' => [
    // Icon provider class
    'provider' => SvgIconProvider::class,
    // The source SVG for the SvgIconProvider
    'source' => 'EXT:my_extension/Resources/Public/Icons/mysvg.svg',
  ],
  'tx-myextension-bitmapicon' => [
    'provider' => BitmapIconProvider::class,
    // The source bitmap file
    'source' => 'EXT:my_extension/Resources/Public/Icons/mybitmap.png',
    // All icon providers provide the possibility to register an icon that spins
    'spinning' => true,
  ],
  'tx-myextension-anothersvgicon' => [
    'provider' => SvgIconProvider::class,
    'source' => 'EXT:my_extension/Resources/Public/Icons/anothersvg.svg',
    // Since TYPO3 v12.0 an extension that provides icons for broader
    // use can mark such icons as deprecated with logging to the TYPO3
    // deprecation log. All keys (since, until, replacement) are optional.
    'deprecated' => [
      'since' => 'my extension v2',
      'until' => 'my extension v3',
      'replacement' => 'alternative-icon',
    ],
  ],
  'tx-myextension-spriteicon' => [
    // Icon provider for SVG sprites
    'provider' => SvgSpriteIconProvider::class,
    // The SVG sprite with fragment identifier (<symbol id="…">)
    'sprite' => 'EXT:my_extension/Resources/Public/Icons/sprite.svg#tx-myextension',
  ],
];