1. Take any one of the fandoms I'm familiar with:
Dresden Files (TV-verse)
Fantastic Four (movieverse)
Star Wars (Phantom Menace)
Star Wars (4-6)
I want to add the two Stargate shows, but I've really only read the fanfic, and done incredibly minimal watching, which means I only know the major characters and couldn't do justice to the full ensemble in either case. :/
2. and give me a type of AU (space opera AU, pirate AU, superhero AU, Ancient Rome, cop AU, etc). I will then explain what story from your chosen fandom I would write for your chosen type of AU.