You have to diddle with the attatchments as well, otherwise they will go wierd and silver/multicoloured. I don't personally understand how the game knows where to get each individual skin from the file, but it seems to work if you create a new texture file and put the texture for your new weapon where the old weapon was, and the new sheild where the old one was, and so on, then redirect the game to that texture file in whatever that file is called that's in the unit model's folder