Ooh, thanks a lot, guys! That helps a ton.
I think I was trying too hard to stay true to the original colorwise. I tried to figure out how much to darken the darkest shades. Then I just tried black.
I turned his back muscle into a sort of second arm to make it look as if he can actually move them. So now it's even more invented than before, but I hope this looks a bit more natural (hardly the right word, but you know what I mean
).
As for demonic anatomy, I wasn't quite sure how human to make him, but I kept the short neck and big hands and feet from the original since I figured a short neck would make his jugular less exposed, and a creature made for fighting would have big hands and maybe big feet for balance. I don't know if that makes sense, though, since I don't know of any ferocious, bipedal predators.
Still some parts left I'm trying to fix, and I need to add shadows cast by wings and horns, but this is it for today.