Modding in the Planes

[Endovior]

Hmm. If you're talking about the standard 'Great Wheel', then it does seem easily doable... just stick the elemental/outer planes around the edge of the map as you desire, littered with appropriate sites, without gates to the 'Prime'. The magic sites that you'd get seem obvious, too...

Celestia: Astral
Arborea: Nature
Abyss: Blood
Baator: Death

You don't really need too many more planes then that... although you could just as easily scatter in the less noteworthy outer planes as individual provinces connecting the whole in a true 'Great Wheel', although this has problems of it's own (Mechanus the only province connecting Heaven and Hell?).

Really, it mostly depends on just how large you want the map to be, and how good your art skills are. It's really the art that'll make or break the map, as the site/critter modding to add the flavor shouldn't be all that hard to pull off.