list_images.php

<?php

$iterator = new DirectoryIterator('images/');
foreach ($iterator as $fileinfo) {
    if ($fileinfo->isFile()) {
        $extension = strtolower($fileinfo->getExtension());
        if (in_array($extension, ['jpg', 'jpeg', 'png', 'gif', 'svg', 'webp'])) {
            echo '<img src="images/' . $fileinfo->getFilename() . '" />';
        }
    }
}