<?php if ( $post->post_status == 'publish' ) {
$attachments = get_posts( array(
'post_type' => 'attachment',
'posts_per_page' => -1,
'post_parent' => $post->ID,
'exclude' => get_post_thumbnail_id()
) );
if ( $attachments ) {
foreach ( $attachments as $attachment ) {
$class = "post-attachment mime-" . sanitize_title( $attachment->post_mime_type );
$thumbimg = wp_get_attachment_link( $attachment->ID, 'thumbnail-size', true );
echo '<li class="' . $class . ' data-design-thumbnail">' . $thumbimg . '</li>';
}
}
}
?>