You have to ask Stefan, although unless you have good GFX there is not much point. As at the moment I your not aloud to use 2002 GFX on PWs. And so you'd need houses, trees etc as GMaps dont do these sort of things.
Also becuase levels would be faily repeative if you didn't have houses etc, and not as intresting as they could be with normal tileset you'd need a good scirpting team to make up for the level lacking. Which could prove a hard job!
Im sure if you can use the 3D Terrain he'd let you use picso.png, but if not, you'll have to be able to make a good Gmap Terrain tileset type thing which is alot more than re-colors and editing which is what most PW tile-sets are.
So it will be a big project, and a very hard one at that.
