Holy poop. Talk about improvement. Glad you've found some interest in digital painting.
My only gripe is that I really think you should spend your time studying the 'anatomy' of the human figure more. I put 'anatomy' in quotes because-- I'm not really talking much about medical-illustrative, to-a-T anatomic memory. I merely mean you should attempt to draw your human figures at more expressive angles. And I can see that you are studying figures-- so it's only a matter of time before it clicks.
Specific things I really think you should work on:
A lot of your figures seem to suffer from locked knees, and washboard torsos. They stand up way to straight-- straight as a board. I really feel like you need to spend more time analyzing the skeleton of the body-- how the spine curves-- how WEIGHT shifts.
Weight's another problem with (some) of your drawings. I noticed a few figure drawings lacked any sort of weight. Biggest flaw? Probably in the feet. The placement of the feet can really fuck up a good, well thought out figure drawing. I can't quite tell how you compute foot placement-- so it's hard for me to suggest on how you would improve on that. All I can say is-- you need to remember that ALL body parts have a STRUCTURE beneath them. To go about conveying weight, think about the supple nature of the flesh. The muscle-to-fat ratio.
Which bringsssssssss me to mah next (and final) point. Heads/craniums. In just about all of your drawings, the placement of your head does not correspond with the rest of the body. This is a common mistake You need to realize-- a head is NOT an upside down egg on a stiff stick. The cranium is a circle, connected to a jaw, a jaw that has different shapes, depending on the person. (Anime has kinda fucked this up. A lot of anime artist base their anatomy off of a stupid egg-head connected to a body)
Things I notice your forget in your facial drawings: The angled area above the brow. It is not a perfectly arced circle. On many people, (mostly men) It's a sharp, almost straight angle.
The area between the bottom of your chin, and the beginning of your neck -- the thoat area. You cannot ignore this space, especially when making a female form. All women have some degree of fat beneath that chin area. The chin ends at the bottom of the jaw, and skin/fat hangs off of it.
Dat's awull I gawt tuh say uh baut dat.