changing artifacts like bg-menu.png -- I know it's not supported, but I just can't find which one to change

So I read: http://drupal.org/node/315753 "force specific image". I am in the same boat, but I am happy copying bg-menu.png over any time the them colors change-- I just don't know where to put it! And I can't figure out where in css or elsewhere it might be getting called..?

Great theme! Thanks for sharing it :D