The only way I can see of making a circlular map is to have a rectangular image, with a transparent circle in the middle of it in it in front of the map. By overlapping other components on the opaque border, you could make it look less like it was a square map with an artificial circular frame, if you get what I mean. Still, I assume you wanted a circular map without any border, which I don't think would be possible (but I'm a scripting noob, so don't take my word for it).