Looks pretty cool. For a more monstrous look you could try making it look like the head is literally on fire, or better yet have them engulfed in an 'aura' of fire as if they were on fire. That would, of course, be a separate and animated overlay though so the base would work fine as is for that.
Alternatively, you can try making the base look more scorched and such by mixing in black and lava-like red instead of yellow.
Just options. I like it this way, but I am iffy about the yellow color and the upper legs//waist/abs could maybe use Slightly more detail to match the chest. Mainly the upper legs.
