Yeah a shitload.http://riafire.deviantart.com/gallery/
And so on. Lots and lots.
There's no "canon" at all though, every time this comes up here people ask, "But what's the canon, aren't Mabel and Dipper fucking in the canon, etc etc," but it's fan made so it's just up to each person. And what there isn't is a definitive comic, or a definitive fic, or any of that, the one up there is just one example of many. Some people just take one or two ideas and chuck out the common ones even.
The common ones are just Dipper and Mabel are evil and in Gideon's place but richer and more powerful, they enslaved Bill who's named Will and sad and blue in this AU, Gideon and Pacifica are good guys and stay at the Mystery Shack as tourists and try to foil their plans, and that's it but plenty of people don't even use all of that (most people don't even bother to include Gideon any more). I think the AU started pretty early season 1 so a lot of characters hadn't been introduced when it first started, pretty much no one shipped Dipper and Pacifica, and so on so it changes and a lot of people just want to have evil Mabel and evil Dipper fucking each other or whatever and use it for that, it's whatever people want.