I agree that it is obnoxious. Unfortunately there isn't much we can do about it (other than complain to mapquest, perhaps, but then the tiles are free).
I could make the tile size larger (four times the total area) which would reduce the clutter, but the watermark would still be there. It's a bit of a development cost for me, without much of a change, so I haven't been motivated. The Color tileset is still pretty good and there is also the hidden GE tiles (message me if you don't know about them).