He's a decent bird. The few things I would want to correct in breeding would be forechest. Ameraucanas should have a "prominent" breast and he seems to be lacking there in this picture. The other thing I'd work on his comb, though I can't really see too much about it at this angle. Looks a little big, but a bigger picture might prove me wrong. His eye color looks dark. It should be a nice bay eye.
He has a nice tail set and the transition from neck to back and back to tail is smooth, with no fluff behind the saddle. Breed him to hens with more forechest, and you could get some very pretty chicks.
The above is just my opinion - others may differ.