I'm plotting up ideas - I think weekly prompts would be good, and compiled on Thedas_Ficarchive - like word prompts. That often was popular in other fandoms. Back in Xmen-verse ages ago, we used to do a sentence challenge. The prompter for that week's item would pick a book, and type out a sentence and those who follow the prompt have to start off their fic that way. That's just what's off the top of m'head, but there's other stuff in the brain to stew over.