yeah, agree with Christoballs, I think mostly the proportions are off. Check more reference material

The jawline going to the chin is odd, good colors though!

hey man, i find lee's likeness isn't quite there yet.
i suggest you work with the full-size ref but also one reduced to the scale you're pixelling, so that you have an idea of what the result will be like.
here's my edit: http://i.imgur.com/pDNPX.png

i like the idea!