-Colorized usernames: I suggest making names colorized by going to Users & Groups -> User Options -> Colorized usernames
-Club penguin smilies: Smilies would be cool, I suggest adding them.
-Contests: Contests are what attract members. Try making membership contests, or WordPress credit contests, that's a good idea.
-Make the sub-forums go into one: Display -> Structures & Hierachy -> Medium (split categories on index)
-Welcome message: I think a message would be nice. Go to General -> Messages and Email -> Welcome email
I'll list more if I can think of them.
Subject: List of suggestions