I can't believe I didn't check out your entry until now. Really beautiful design! I also happen to be a sucker for warm tones and fiery themes, this is some great eye candy to behold. I like how the contrast leads the eye to the center of the design.
My only concern is in your final illustration making sure that the character reads clearly. In the most recent image of the full concept (I understand it's just a concept sheet and not the final illustration) I find it slightly difficult to make out the facial features, just because of the molten lava oozing down the face obscures its readability. I worry the design may be a little overcrowded in a few places?
To be quite blunt it is a nice illustration of your design but as a reference sheet/character design sheet it's a little hard to read or see where everything is, if that makes sense? For such a complex design I feel it deserves full on front and back view concepts. But that's not really relevant this time around because they are only going to be looking at the final illustrations.
All in all a wonderful and red hot design, keep up the great work!
(also don't forget we gotta clearly incorporate the emblem in the design somewhere, if it is in there and I just didn't see it, my bad!)