Optimus Drawing

A pic of Optimus Prime I drew a few days ago. I know his head's a bit squished, but I was running a bit close to the edge. Any ways to improve would be awesome, if no one minds. Always looking for Constructive Criticism. Partially taken from Transformers, Police Action. Forget what series it was part of tho. I don't own Transformers, I think Hasbro does.