Well my texturing is rubbish as i can't deal with UVs to save my life, so i can't help there. First, i'd give him more of a nose as it seems a little short for a great white and they also have nostrils. Then I do think you should model the eye and not just texture it as when you think of sharks it's their big black eyes that come to mind, well and teeth. Talking of teeth i'd say have fewer and make them larger as great white tend to have large teeth and just fewer of them (still too many though).