Agree with Blackstar, don't do pop-up ads. Hate them.
Simple and pure design with simple colours is good.
Make words easy to read too.
Skin gallery is awesome idea, wanted that for ages.
Keep retaining the search function as well as the new posts search.
Also, a more interesting and better "rank" system - right now it's just New member, Member, Senior Member etc. etc. Make it more interesting
(i guess thats a small thing but just a suggestion).