Just a few thoughts
You light source, as it looks now, is from behind the knight? If this is how you want it, I feel like the front of the knight should be a bit darker with most highlighting being done at the top of the head, shoulders, shield and sword. Your higglighting appears pretty correct, but I think his front is too bright for the most part. Also I think the would be some space beneath him, not just shadow, with the angle it appears your light is hitting him.

I did a quick edit to show a possible light source, as well as the current with a new helmet and an alternate helmet, but looking at it now the left helmet makes him look to his left (oops). Also I moved his forward foot up a pixel in the left and his back foot down a pixel in the right, I just felt like they needed more space between them.
Finally I grabbed all your colors and I think You have a few extra gray's that maybe you could combine a couple? Maybe not, but nevertheless I don't think you need the purple in the shirld emblem, I think one of your blues might do fine. But this is all just my opinion. Nice work
