I agree that making the prompts anon as mandatory is really helpful - it gives the impression that various people are seeding for their own desires even if you're doing a bunch yourself.

I also think that having the rules for prompts be relatively broad is good. One of my fandoms has a meme that's specifically kink-only and I find it pretty off-putting. Not that I don't like kink! But that's not usually the locus of a story for me and so it makes it difficult to be inspired by anything. It sounds like your criteria is already pretty broad so you're good there, but just wanted to mention it.

And yes, AO3 collection!