I like your characters you have been working on.
If I may, One thing I'm learning now that never occurred to me before with characters is that you have to think about your character from the base up. How the bones shape theri body, how the muscles then further shape the body. Fat difines the boddy a lot differently to muscle and finally, how is the skin stretching and tightening around the underlying layers.
For instance, take a look at the face you sculpted. First think about how the underlying skull would define the face. how the jaw bone would define the bottom of the face and the flow to wards the chin.
Check out these two links blow.
Do you see how the jaw line shapes the face.
One is very broad and the other is more elegant and narrow.
Have a look at their chin, Emma Watts has a bit of a bubble chin where as the first women has more of a slender chin.
Check out their cheeks.
The first women has bigger cheek bones, which causes her to have those rounded cheeks with the dimple underneath and Emma has more of a flatter cheek bone.
Look at their noses, Which is shaped by their cartilage, (Obviously lol) and finally their forehead. See the differences ?
Now I do believe that these things are key to character creation and its never to early to start learning the fundamentals, this is why I havent attempted a human character yet. You font want to form bad habits and then try to correct them, this will take longer.
So get into the anatomy and proportions as soon as possible.
I highly recommend this book.
Apologies for the long winded message.