Ok this is what I've done and we'll see how it works.
Members can upload files no larger than 100kb in size.
Members can upload in the following forums: Fanart/Fanfiction, The Fridge, Silver Screen, The Party Room, and After Midnight.
Pictures are the ONLY thing that can be uploaded provided they are in the jpeg format. This is not my rule--invisionfree does not allow anything else. I've tried gifs and they don't work all the time.
We'll keep this up for a while, and I'll watch over who's uploading and who isn't and go from there.