Forgive me if I'm wrong on this I'm not an expert. Though I still can appreciate these practicing papers, it looks good in particular that you've a pursuit of difficult angles and contours. You've either a hunger to learn or genuinely enjoy doing it, or both. It looks very good.
But, are the lips not too well defined in terms of dark pencil strikes, or are the lips less concentrated on and therefore less deliberate in terms of their structure?
I say this because they're not quite claymation mouths, but rather it's as though every character has makeup on somewhere in the lip region. If you were to look at various historical coins and the way the illustrators have defined their mouths, I imagine theirs would look more abstract than yours currently do and the purpose would I'm guessing be to avoid that effect.
It's just something I thought when I looked at these. I'm a moron who can't draw. Thanks for your time.
Oooh look, nudie girls