Take a look at my first HL2 DM map....called dm_inbound , a large dark map, built with blood and sweat, a real man's map with secrets and a nice trap (see if you can find it) Has taken a long, long time to make and optimized as best as I could.

I purposely made it a dark map (actually the screenshots show it to be darker than it is for some reason) for the idea that it can be played stealthy with plenty of hiding places. It makes a good TDM map, as certain areas can be controlled, however it is a pretty big map so you may need a fast PC to run it with a few players.