Actually, lightgamma values anywhere above two make most maps start to look like crap, except for the absolute darkest ones.
What might be really fun some time, if ew can get a lot of trustworthy people on, is playing a game where everyone has lightgamma 5 set. It makes the maps DARK. But the NS gamma overbrightening effects look awesome. The colors stand out so vibrantly. And you really can't see a THING in most dark shadows. Bast is a great map for this. You really have to run around with your flashlight on all the time, and you've got to move in squads, as ambushes seem to be waiting behind every patch of darkness.