Yeah, these are pretty nice. To improve, i'd reccommend working on Anatomy and proportions, there are plenty of tutorials on the net and deviantart for that kinda thing.
Also, a little thing to think about, hands are about the same size as your face, if you put yours up to your face, you'll see. :3 so yeah, make them a little larger than you do at the moment and you'll soon be even better than now! :3
ooh, if you're feeling advernturous, why not even try drawing from various angles on their faces theyre all facing forwards besides one, so maybe a new angle would be interesting for you too!
from these i can see you're talented, and you have a really wonderful creative mind, so keep it up, keep working at it and you'll definatly be a name to remember! :3!
