I'm sure looking forward to seeing this!
This is something I'll definitely be doing a lot of, now that I know how to handle it with the lights. I can see myself building a lot of dungeons this way, and making dark corners, and having things come out of those dark corners...
I remember playing System Shock for the first time, and when you escape that first room (hospital bay) and get out into the first corridor, it had really dark corners and such. And though there was light in places, you had these really pitch black areas ahead of you. Well, that just happened to be where the mutants spawned, and so they'd rush at you out of that darkness... I about crapped my pants.
This particular dungeon.. it's small (by my standards), and was really supposed to be MUCH smaller, but I enjoyed tinkering with this tile set, so it grew. Then a quest idea happened, and it grew some more, and now it's something that should occupy the player for a few minutes anyway... If I can work it... those dark areas will be really useful.