David, you can simply checker the butt, and the plug will be invisible. Makes it easy to chip the toe though.

Another option is to make an ebony butt plate, match it to an ebony pistol grip plate, and add an ebony wedge at the front of the forend. You see this more on rifles and combination guns, but I would think it beautiful on an OU as well. Rosewood would work also, as would some other really hard woods.