You've definitely got a handle on values, texture and abstract composition. The last piece especially has some really nice shapes going on.
I think that across all of these there are a few things you can work on however. For starters, none of these are particularly finished in my mind. Perhaps on some of the concept art ones like the image with the different hairstyles this is fine, but for the illustration pieces I think they can use more tightening up. Look at Craig Mullins--yes, he does have a more painterly approach and uses texture and atmosphere much like you do, but if you look at his finished work he gets a much tighter image than his speed paintings. Right now your stuff looks more like tight sketches, but not finished illustrations.
You can stand to study anatomy and structure a bit more. Currently in the first pic and the one of the different hairstyles, the anatomy and the structure of the faces are not very good. The face is quite generic and not very realistic in terms of planes and structure.
Finally I would like to see you step out of your comfort zone in terms of colour more. You can paint this murky earth tone type stuff with overcast lighting very well, but you do not seem to be very versatile. I would like to see some different lighting situations. Try some stronger lighting, some back lighting, some more saturated pieces, some done at various times of day, whatever. Play around more with it, as currently you are painting in an almost monochromatic manner with all the paintings having very similar palettes.
"Complacency is the womb of mediocrity. " -- Jason Manley
"If you always put limits on everything you do, physical or anything else, it will spread into your work and into your life. There are no limits. There are only plateaus, and you must not stay there, you must go beyond them." -- Bruce Lee