Map Ideas?

I would like to make a map, but I have no idea as to what it should be. I want it to be a map where like 2 people spawn on this side and 2 people spawn on this side. But that would make it impossible to play on single player. I will make a map like that though, if you guys want. I just have no idea as to where the map should take place.

Maybe a church or Catherdral, with an underground passage of some sorts. I started one like that, but it became a bit dodgy.

Or, like me, base it on a Mw3 or Mw2 online map? Thats a good way find something to do, just copy XD.