You're a VERY talented artist. Your style reminds me ever so much of Bendover. I like the way you've defined everything. Your shading is very accurate with regards to the shape of the shadow in relation to the object creating the shadow. Your blending is fantastic. What I'd personally do is add in some contrasting highlights of brighter green streaks here and there which is what you seem to have somewhat done already. Also maybe add some more elements to the head texture itself like create some back design and map it all the way round. Any chance I could see some previous work?