OMG! That's great!
You have a really nice style there - the brushstrokes you use really help to bring out the specular highlights. Great detail around the eyes.
Some small crits for this particular image is that there is a dark halo around the tounge (in fact, it looks like it goes round the whole face) which makes it look like it has been cut out of some thing. Shouldn't be a major problem to fix.
One crit for future paintings... have a look at adding some blues and greens to the skin tone. Right now it looks ok - but you'll be surprised as to how effective a blue shadow or a slight green to a skin tone is. When I was at school I remember looking at some of the 'old masters' paintings and realised they were probably on to something