I have so much trouble drawing hands... but transformers hands take the cake. I think it's the weird forshortening you have to do on them. Same with their limbs... that's why my pics don't have a whole lot of fore shortening or detail to them. XD
Anyway. I built a 3d model of a transformer/mecha hand to help me draw and thought I'd post some of the renders to help other people as well. I put it in stock, but it's really intended as a drawing reference. I suppose you could do image manip with them but it's not really made for that(black background will swallow up shadows). At any rate have fun~
If people like this, I'll be happy to do some more poses or renders. :3 just ask.
Your render looks amazing and gives you and idea on how to articulate and decorate them, in the case you want to give more life to the hands.
Thanks for sharing.