Open games make it easy - and legal - to fuse wildly different ideas together. I'd love to see a setting made up of open elements of all sorts. Monsters from D&D, races from The Shadow of Yesterday, gods from public domain books, superpowers from 4C System, whatever!
I think we could create a setting like that by each proposing an element from an open game, public domain book or the like. We'll end up with a strange setting perfectly legal to use.
My element: . We have to be careful here, because though Lovecraft's work is public domain, that's not the case for all the authors who built on his work.