I think they are very good alla prima studies. I’m not sure what you want to work on. One thought is that you could work on edge variation, most of the edges I see in your examples are consistently similar some edges should be sharp, some soft, some lost. This may add interest to your work, allow you to emphasize areas , and add a technical challenge which you’ll find engaging.

Hey David, One of the issues has been mentioned, edges. Not only the edges between forms, but also edges between values. Another issue is your shape design. You have some shapes of values that don't really describe anything. Also, some of those shapes are the wrong value. This causes confusion for the viewer because a different value equals a different plane. I'm posting an example so that you can see what I mean, I hope it helps :)

I really like the painterly approach here. They look like traditional medium. My suggestion is to begin focusing on edges. Most of the edges throughout the paintings are very hard when life has a myriad of sharp to very soft edges. I know Richard Schmid in his book Alla Prima gives some wonderful instruction on edges. I think Proko and Jeff Watts touches on edges quite a bit as well. The next suggestion is to play with very subtle value ranges. You do this really well with the painting of the woman with black hair in sunlight, on the cheeks. Most transitions in the other paintings though are all very abrupt and turn the forms too quickly. They tend to look more like hard edges rather than undulating bumps in the face. Lastly, detail. I think you can take the skin of these paintings much further. Really get in there with the details of the face and introduce more color ranges. It looks as if most of your skin tones are based on a single "mixture" and then adjusted in value with black and white. You can expand your range subtly tremendously by using color to transition value rather than black and white. Robert Henri in his book The Art Spirit talks about this a bit. Probably the best suggestion I could give you is to compare your work with your most favorite portrait painter. What are they doing in their paintings that you can copy? How can they influence you to take your skills to the next level? Art is an infinite game and infinitely rewarding as well! You got some skills here, keep working hard at it, pushing every day and I'll you come up with some amazing work! Thanks for sharing!

Well, what is the result you want? I think these look good, they have a certain style. Kinda like realism mixed with something. I feel like the first one is the most realistic, but the others have more style.