Simple Wordpress function to get the attached images that belong to a specific post.

get_attached_images

// get all attachments from a post, except the featured image
function get_attached_images ( $post_ID, $featured_image = false ) {

    $args = array(
        'post_type'         => 'attachment',
        'posts_per_page'    => -1,
        'post_parent'       => $post_ID
    );

    // do we want the featured image?
    if (!$featured_image) {
        $args['post__not_in'] = array(get_post_thumbnail_id( $post_ID ));
    }

    $att_images = get_posts( $args );

    return $att_images;

}