Ian, these have got to be one of my favorite animals! You got tons of detail in his face, eyelashes, head "knobs"...and the patterns are beautiful as well. You might try opening a shadow/highlight adjustment layer to bring out the right side of his face a bit more and I think a slight boost in contrast at the dark end of the spectrum would help as well. It feels a little monochrome or a bit flat at this point. You might also try adding some blue to the white BG to see if you can add a bit of color there as well.
Overall, lovely image...a little better head angle with more direct eye contact would have been nice but this is very close and certainly a keeper.