Hey man, great work and thanks so much.
My one suggestion, the comment popup is confusing. I know when you embedded comment you started to get spam, but something like
<a href='index.php?showimage=<IMAGE_ID>' onclick="window.open('index.php?popup=comment&showimage=<IMAGE_ID>','Comments','width=480,height=540,scrollbars=yes,resizable=yes');">Click to leave a comment</a>
might be a more noticeable solution