You can create a new map that only has unit images, and depends on another map. Say you wanted a revised mod with mexican units. You create a map called revised_mexican, in a folder called revised_mexican, with a units folder, a games folder containing your new game, and a file called dependecies.txt. dependencies.txt has one line, which says, dependencies=revised When the game looks things up, it will first look in the revised_mexican folder, then the revised folder, and finally in the images folder (all maps have a hidden dependency on images). yes, the map name is revised_mexican.