You look fine on that horse. Nothing to worry about!
Now if you were trying for the "look" of English/Dressage - which I doubt you are - then you would want a taller horse.
I disagree.. If he did dressage, he'd be fine. Hunters would require shorter stirrups and jumping too. He could (if he wanted to) manage English just fine. The trend is taller horses though, but honestly shorter ones can do English just as well :P