took me a minute to figure out what is your question...
It seems 4images does not support this...(me surprised)
But try this:
in includes/functions.php find:"thumbnail" => get_thumbnail_code($image_row['image_media_file'], $image_row['image_thumb_file'], $image_row['image_id'], $image_row['cat_id'], $image_row['image_name'], $mode, $show_link),
Insert above:"image_url" => ($show_link) ? $site_sess->url(ROOT_PATH."details.php?".URL_IMAGE_ID."=".$image_row['image_id'].((!empty($mode)) ? "&mode=".$mode : "")) : "",
Then in thumbnail_bit.html template use:
{if image_url}<a href="{image_url}">{endif image_url}{image_name}{if image_url}</a>{endif image_url}