Lewk, you might want to give him something to improve upon, not just trash what is there.

I think that you should try a render that has more action in it, those types are hard, where it is just a person from the shoulders up. The square brushing doesn't look very good, it just looks a bit grainy and pixelated, I would try some more natural brushes. I like the colours but as said before it's hard to get this type of render to fit with anything. Good try and it's all just a learning experience, read some tuts and you will get better.

A really hot tut right now, is Immortal's Prepare for War, I would try that one, it's a great source of info.