Yea, maybe make the crystals in the immediate background (foreground?) a slightly more orange tone, bringing up the brightness on the faces and saturation on the edges. That should help give it a warmer look and add a touch of life.
If you made everything (not the crystals or torch lights) darker, then that would give a more ambient look, too.
Fire doesn't emit white light, maybe make the glow a more yellow/orange?
OMG that looks effing amazing! This is exactly what i was getting at - look at the depth?! You could go for miles and miles with that background!! The lighting is good and i like the idea of the runtime effect you mentioned - try it and make a video so we can see it in action (don't want much, do i?!)