Any interest in playing not on a flat square but on a three dimensional sphere?
That would be very cool and a thing I thought about sometimes, if you mean it is still two dimensions but represented on an orthographic projection, with the user scrolling the map like you are handling a globe.
My suggestion, on how it should work, is that the map-maker should provide a map supposed to be drawn in an equirectangular projection and also provide the four coordinates of longitudes and latitudes at the edges of the input (global maps will have the same longitude entry for both instances or -180 and +180 respectively for one and the other) so that the program gives the ortographic projection for the map. The user may be allowed to switch between equirectangular and ortographic, and other projections may be supported too (The mercator seems to be popular amongst TripleA map-makers, and I think it is the one used by the "World At War" map, although I believe it is a not very good choice.).
If you mean three dimensions, that would be great for futuristic space maps, but I'm not personally interested in such matters.