Just throwing my two cents in again, haha.
I was thinking about the problem of either having or not having prompts for No. 6 day. Personally, I think that I'd like the inspiration of such a prompt. Even something as small as just, Shion's Birthday. (I know that was mentioned. And I like it!) As for the other days, though, what about them?
Well. It occurred to me: why not start a thread here, with prompts and/or art requests? Like, somebody could go into that thread, say, "I really wanna see writing on this topic!" and then on No. 6 day, the people who want to participate can just go to the board, look at the suggested topics, and say, "Oh, that sounds cool. I like that idea. Guess I'll do that." That way people who want certain art have a chance of seeing it without having to contact an artist directly if they're shy, and the artist gets a source of inspiration.
Of course, doing an idea from this board wouldn't have to be limited to No. 6 day. It's just that, since No. 6 day is the marked-out time for doing fanarts and writing for No. 6 anyway, at least you'd have the board around for those times when you feel like participating.