normally, i would comment on the confusion created by having cool lights and warm shadows, but i think in this case it perfectly shows the 'magicalness' of the creature and the irridescent qualities of abalone. if you can't tell, thats a strong compliment from me ^^
AS far as helping with tones, the c64 palette is a tricky one.
from what i can see, you seem to be missing a color. i guestimated it, since i didnt have time to really caluculate exactly, so heres my rough edit:
i just mixed that rich warm (by comparisson) brown into the chest, and part of the wing. if you like the look, you could do something like that either across the board or just where light hits directly (the latter might be better) or use it only where light does not hit directly(which might be best)