I downloaded a map on battlenet one night called "Triple Defense" it had a custom tileset and a interesting layout of to teams, but they weren't against each other; just like to td's going at once. It is a very nice TD. But since i'm on 56k and it is slow download for me to host, i can never play it.
Also the map has some rather prejudice content, against nazis or something i dont remeber. I have never seen anyone host it, cause i dont think anyone has it. But it is a good td.
It features lots of towers that have special targets, kinda like massacre td, where certain towers only attack heros.