For lighting, your best bet would be to use the sunlight feature. If you only want to light specific areas, well, you're pretty much limited to adding lights.
As for detail -- I think what you need to do is try to make the rock look more like rock. The best way I've found for doing this is to throw some blocks up against the walls and start slicing chunks off of them with the clipping plane tool (much like slicing chunks off of a block of cheese with a knife). For an example you could look at the bombsaway .map file I posted (search the forums). The layout is extremely simple, but with a few clipped brushes, it looks a lot more natural.
