add_shortcode("contest-thumbnails", "show_all_thumbs");

function show_all_thumbs() {
    global $post;
    $post = get_post($post);

    /* image code */
    remove_all_filters('posts_orderby');
    $images =& get_children( 'post_type=attachment&post_mime_type=image&output=ARRAY_N&orderby=rand&post_parent='.$post->ID);
    if($images){
    foreach( $images as $imageID => $imagePost ){

    unset($the_b_img);
    $the_b_img = wp_get_attachment_image($imageID, 'thumbnail', false);
    $thumblist .= '<a href="'.get_attachment_link($imageID).'">'.$the_b_img.'</a>';

    }
    }
    return $thumblist;
    }