wurfel almost said it all for me already ..
.. I especially agree with smoke particles over the lava enhancing the athmospheric feel of that part of the map - while on that subject: it feels like a few more breaks in the walls, like some torches at least or some alcoves with statues/ornaments/what-have-you, were all that's needed to make this into a classic-to-be - meaning I'd like to see it in the official set!
details, details ... oh yes, ... those pieces of tiling littered about the map ... mmh, well, where do they come from? Shouldn't they be indented/missing rather than ... well ... some Alzheimer ridden castle constructor having forgotten half his work materials after finishing the job so nicely?!?! You know what I mean?
And the absolutely last iota would be for the lava-tunnel to not end so abruptly, sure you never really get to look into there while fragging ... but just as that final touch ... some grating at least or so, where I can imagine the lava keeps flowing ...