I have found that shooting photos in caves to be difficult. This photo illustrates part of the reasons why. Using a flash in this environment, you run the risk of overexposure. Sometimes it's hard knowing if you are looking upwards or at a wall.
Not exactly low key, but I will say that this would be much better with that flash glare on the left cropped out. I'm happy with the square crop on some of my pictures. This might be slightly improved that way.