I'm wondering why you have all these shades of each colour, but no real solid shading aside from the hair. I mean, if you wanted him to be flat-looking, then by all means, you can ignore me. (I'm not being rude, honest! I'm just saying it's fine by me if you didn't want shading.) But I did go ahead and do a little edit. Now, I'm no expert, so I can't really do a whole lot, but shading is my favourite part.
I added wrinkles to the shirt and collar-thing, as well as highlights in the hair. I didn't change the shape of it, though, which is something I feel it needs... Also, you have extra blues in your pallet that are not used.

My last point is this would probably benefit from a light source. You have three that I can find!
On the legs and arms, it comes from either side; on the pants, it comes from between his legs; everywhere else, it comes from straight in front of him. I think I managed to unify them in my edit. When I was about to save, though, I realised his face had a different light source, heheh. But I changed it.

I was then going to up the contrast, but I was afraid it would change the feel of the piece. He seems really dusty like he's been traveling a lot.
Anyways, here it is. Hope this is at all helpful.