When you go to search member galleries, for example, above the search space is a 'home' in purple letters. If you click that, you get a search page with the options to choose 'keyword' or 'username'. The url is here: http://images.cosplay.com/gallery.php
I had the same trouble for a while, but now I know where to look.
Once again, if you click photos above, then member galleries, then home, you should get the url I supplied with the Keyword option.
Good luck, I hope my explanation helped you.