I typed up a big thing earlier but my computer fucked up and I lost it
Anyway, this is just a small edit to show what I meant about the selout on the shirt. I also got rid of a colour (the brown which outlined the arms/part of the face) and replaced it with the darkest purple (they were virtually the same).
Can't really help you with the ambient lighting 'cause I'm only new to it myself (never really attempted it in any significant way before). Think of it this way, though: the strongest light source in this pic should be the flame, and your shading/highlighting should follow suit. As it basically does, you should really just try adding a purple-ish tint to the highlights, or something like that. In order for ambient lighting to really work, your initial light source (say, the sun) should come from a distinctly different angle (geneally, like, the opposite side). Then you add the secondary light (the flame, here) and it all gets very confusing and my head starts to hurt.
like I said before, very nice pixels. I love the linework, the forms, etc. and look forward to seeing this piece progress.