Ok, so let me see here. I loaded up RTW vanilla and there's that map thing. When I select different factions, I see a different map image.
Call these MapJulii, MapScipii, MapBrutii
Can you take an imagefile of a Macedonian pike line, and replace MapJulii with that, -then- an imagefile of Seleucid cataphacts and replace MapScipii with that, etc?