I don't see how it's crowded. A quick glance at the forum shows that your competition, the Graphic Competition, and the Music Competition are the only competitions that are around right now. That isn't a lot. Another quick glance shows that you are taking an unnecessary step in the competition process - a sign up thread. There is no need for that and people should simply submit when the theme is voted on and you post a deadline. That may be a cause of some of the clutter that you are seeing.
Adding sub forums to it is entirely unnecessary. It reminds me of when we had a Sign-Ups sub forum in Fan Works, which was never very active because only a small circle of writers ever use sign ups. There's no point to separating the different competitions when
- There aren't many active competitions
- Past competitions are buried fairly quickly
- There are distinctions between which thread is covering which competition
As a former administrator, you should remember the KISS method - Keep It Simple, Stupid. Adding more forums than are necessary is a bad idea, because then there are too many forums with too little discussion. Spreading out discussion when needed is good, but when a forum isn't particularly active - like the Competition Forum - there's no need for it.