Oh wow. That looks like a job for photoshop...
But things that you might look into-
There's EL Sheet, EL tape, and EL wire out there that can create evenly lit areas, bars, and lines, respectively. They aren't very bright and if you want a lot of it, it gets expensive. Also, you'll need to hide battery packs somewhere.
LED's are awesome, but if you look at them directly it's hard to avoid having pinpoints of light. You might be able to make the crusty-dark-magma sections to hold little LED's that would shine onto the firey bits to light them up.
And just as another thought, although I don't know how to make it compact enough, but there's a popular artificial flame effect (this
) that involves a blower and a piece of silk. The blower blows the silk up and it makes a bunch of ripples, and a few colored lights at the base play on the silk making it look like fire. If you could figure out a way to get lights, blower, silk, and batteries all together in that super skimpy costume you'd have something really amazing.
These are all pretty expensive and probably impossible ideas. So, of course, now I want to try them all.