list_images.php

<?php

$files = scandir('images/');
foreach ($files as $file) {
    $extension = strtolower(pathinfo($file, PATHINFO_EXTENSION));
    if (in_array($extension, ['jpg', 'jpeg', 'png', 'gif', 'svg', 'webp'])) {
        echo '<img src="images/' . $file . '" />';
    }
}