Although I think GW-style hair is tough to paint all the time, your ork's red top-knot is really splotchy, rather than looking like strands. Also, the fact that it's the exact same shade as the red bits on the bike doesn't look quite right. The red on the bike could be shaded more as well. Your green flesh tones and metallics do look pretty nice though.
The photo appears to be washed out, the reds especially lack depth. The whole is also lacking contrast as the base is grey and the bike is mostly metal and black. Additional brass areas would help to give some additional contrast.