Pretty much what these guys have said. I think looking up some helmet references would benefit you, for the helmet calls for a total re-do.
Face is cool though.
. . . that's the one thing. another one is that the expression looks unnatural, kind of forced -- I like your take on the anatomy (esp. the eyes came out pretty well) but it still lacks some more solid construction the whole thing should be based on. the helmet is a big no-no.
the face is good, but it doesn't feel like the face is in the helmet,
Fun palette - but you're not even using the right colours; lucky I'm being generous and using a tolerance of 10.
Anyway, looks good, definitely an improvement over what we saw in the forum.