Nice job so far!
While all the features are well mostly well proportioned, they could use some shuffling around.
What stand out most are the eyes, they are too far apart, and maybe too small. Start with the general rule of a head being 5 eyeballs wide, with numbers 2 and 4 being the actual eyballs. Once that is established, you can then take your creative license to customize things.
Then I would suggest taking each feature and really looking at some refs to see what details you may be missing. Not to pick on the eyes, but it looks as though you have started to draw in some eyelids, but they need some more work.
Again, its a good start! Keep it up!
Darren