His teeth look a tad flat.  Changing the shading to give a rounder feel and changing the shape of his right tooth might help.  Also, that indent under his nose (does this have a name?) is too prominent.  It should only be 1 shade darker, but perhaps a bit bigger, too.

I quite like the concept, though.  There's just something really hilarious about an orc in bussiness casual. 

This looks pretty good, man! I specially like the way you used a dithering-like technique to make the transition between light and dark areas!



Couple of things could be smoothier, though! The hard black outline it quite distracting - maybe try using darker shades of the respective main colors? :) Also, shading on the ear looks a little bit off. Other than that, great job, man :)