[David Johansen]

It's not as detailed as most rpg settings but you might want to take a look at Fantacide by Rick Priestly, Andy Chambers, and Allessio Cavatore. It's a flat world with a hole in the middle surrounded by The Great Waste of Time. There are winged monkeys with blunderbusses, native American centaurs, the hungry woodlands, and the creatures that claw their way up from beneath to eat your skin and eyeballs. Great place to wander into through a portal or just fall through the hole in the middle.

Anyhow, you could always just use Middle Earth and watch the pure fans squawk and squeal as priests of Thor throw death spells at beholders. :D