I really really like your style.. its somewhere between anime and realistic, and simple yet professional. ^^
Overall, what's your aim? It seems like you want to make some comic/cartoon/manga things since you're paying more attention to the same characters in different poses / moods..
Since you are kinda developing your own style, I really can't say much about proportions and ratios, but still I think the nose needs a little more work on it, those have to look very much the same in all drawings unless there's a drastic pose change.
That's about it, you should try to create a full complete drawing though, possibly a scenario with 2-3 characters from a rather unique camera angle, there I will be able to notice more of what you're lacking..
You should also watch
Mark Crilley on YouTube, he explains exactly what you're doing :)
Thanks for the feedback. :-)
I was thinking about making a comic to force me out of my comfort zone when drawing but I'm not a writer so that makes it difficult. I tend to focus on faces when I draw and don't often draw much else. I do need to branch out a bit more and when I do I'll post it.