I've just seen a cosplay-related question, which was posted during the definition-phase.
http://area51.stackexchange.com/proposals/31538/anime-manga/31755#31755
There was a discussion, whether the question would be too objective, but I have an other question: Are cosplay-related questions on-topic in general?
I know, that a cosplay is always manga/anime-related, but isn't it more a question about dressing/photography? I don't know what question could come up, but I think, that cosplay-questions are most likely something like "How should I dress" "What's the best background" (See Photography.SE) ...