After a year's break, my art is rather rusty again, and I could really use some tips, especially shading because its the part I find most difficult. The sprite is just the head for the moment, I wanted to get it right before moving on:

I've been studying various photos and things trying to get the shading right, but it still doesn't look right to me, and I can't figure out why. Suggestions would be welcome. If anyone wants to do a paintover, thats ok, just make sure to list exactly what you changed so I can try it myself. Also, if it takes more than an hour, don't bother, I have a full time job now, and want art that looks ok and I can make fairly quickly, rather than brilliant stuff that takes ages.
Thanks in advance

I've been studying various photos and things trying to get the shading right, but it still doesn't look right to me, and I can't figure out why. Suggestions would be welcome. If anyone wants to do a paintover, thats ok, just make sure to list exactly what you changed so I can try it myself. Also, if it takes more than an hour, don't bother, I have a full time job now, and want art that looks ok and I can make fairly quickly, rather than brilliant stuff that takes ages.

Thanks in advance
