@impss,
- make a new thumbnail_bit for you new images ... !
- make a copy of your thumbnail_bit.html, edit this thumbnail_bit.html for your needs and save it as thumbnail_bit_new.html
- now you can change in the index.php
$new_images .= $site_template->parse_template("thumbnail_bit");
to
$new_images .= $site_template->parse_template("thumbnail_bit_new");