I recognize that triangle from the OGL tutorial program in DevCpp
anyways, I think it's a clever idea... one option would be for the XML descriptor choose a specific series of models to cycle through... just a cool spinning model in the background... I don't like how generals has like a whole game playing in the background while you load the menu... also, a bunch of people have whined that loading the whole spring engine into memory just for the sake of the gui would be annoying, so make sure this gimmick doesn't break it...
one idea for 3D would be to make an acctual 3D interface to map to the buttons, perhaps on the side of the cube... it would look flat but when you clicked a menu item the cube would pull back, rotate, and then present another face...
or if you can load a map into memory pretty easily without loading any pathing or units you could have a fps style view spinning in the center of the map ... could be cool...