The main subtract for your map is not square. It's uneven.
People are going to get boosted out of the playing field. Add a physical volume just around the lava to kill players. It won't work correctly (hope the fix the bug in 2.0) but it does work somewhat- the player will die just slower.
Switch the screen to the other side where it can be higher on the carver wall. It can be better seen above the fence.
Lava glows by itself. I would suggest you play with the lighting so all the lava has a slight glow with brighter spots as you have it now.
Some grates in the floor showing the lava below might look cool.
The fire emitters are much better. Check out the fire emitter I used on DB- Dragon Isle:
http://www.pcgamemods.com/3216/, they would work good for your map also. Maybe a combo of yours plus dragon isle would look nice. Spred the fire emitter out between normal, high and supper high detail. You only have them on normal and supper high currently.
Your goal volume should be 40 units behind the front of the goal. Yours is way to close allowing self goals and non-goals.
Your PBox is very small. If you size it to standard maps it needs to be moved out. Grid on 16 - yours is four main grids out, standard is 6. In any event, I think it needs to be be moved out further.
In the deeper side cavern you have a fire emitter on the center land. - looks odd that way.
You have only one sound. Work on the sound. A few sound sounds spread out will give the map a better feel. There are cavern sounds in the editor you might want to check out. Use it or something else for the overall sound. Move the fire sounds to the fire emitters. A bubble sound for the lava fountains might work.
You need some goal events. The drangon fire I use in DB-Dragon isle might work for you map as well. Coming out of the light by the side of your goals with the color adjust for red/blue might work. Or put something on the caver pillars and have the effects come out at angles like dragon isle from there.
Hope my comments help. Very nice map.