if you want to get better try using a different ref-- ex--
http://ts4.mm.bing.net/images/thumbnail ... ab61e41e9e try drawing that untill you think it looks really good, (it doesnt madder how long it takes as long as you practice) then get another photo and draw that one untill its right, and it helps if you use all the tools, not just the brush and paint bucket
im not saying you work is bad, but i got better by practicing and i practiced on all the body, not just thehead. it helps if later you need to draw one with a body.
sorry if you dont like this post, just trying to give some hints on how to get better.
it is good btw