Thanks A,
I am using some very faint lightmapping right now; just enough so that you can barely see the areas outside of the torch light. I haven't used any lightprobes yet, but I'm about to start experimenting with them. I'm also entertaining the idea of throwing a few braziers in there just to give some variance to the lighting, but I want to be careful not to reduce the spookiness by doing that.
The zombies look a lot better when they have a secondary light source on them!