This may be asking for too much, but an underground mine with minecarts that you can ride in and shoot from and everything.
Or, a map where instead of being (for the most part) horizontal, the setup is vertical. I'm talking about a map where one team's base is higher up than another's. There are many different floors that you can fight on.
Yeah, something like that.
Also I notice that Convoy sometimes plays music. I'd like a map where there is dead silence in the spawn area, but as you approach the action, the TF2 theme music gets louder and louder!