Hmm...I can understand why you'd want that but I think it would be best not to do that for this round. Allowing 'fandom, chara 1/chara 2, any' could get redundant (especially for bigger fandoms!). If you're worried about making prompts too limiting, try and stick with simple and vague one or two word prompts.

We might do something for small fandoms later on if the first round does well though. :3