Anyone here remember LLoyd Alexander's world of Prydain? Always thought that would be kind of cool. (The Cauldron-borne would lend themselves well to some kind of godwarsish hack-n-slash, but the world also would have much potential for RP)

And then there is the world of Narnia, which C.S. Lewis developed with such detail it's right up there with Middle Earth.

And while it's certainly too scant to make even a full area, much less a world, I would like to see at least some scattered objects inspired by the poetry of S.T. Coleridge (At the very least make an albatross necklace that isn't just yet another stock noremove item)