In the first picture (Artist Nesterov Mikhail) I liked a rhythm and balance.
In the second picture (Artist Michelangelo Merisi da Caravaggio) I liked the focus the human face and economy painting.
Time spent an hour on each.
These are coming along really well. You are very talented. moving forward, please pay very very close attention to your use of values. You are getting your levels off just a little bit, and are sometimes missing your lightest lights. I would suggest going back through your images and spending 5 minutes each on adjusting the levels and value range. It is so close. I just want to push you to be perfect on value control as it will pay off on all your other paintings you do from here on out.
much better. Try integrating a bit of a textured brush when surface is obvious in the originals and secondly be sure you are getting the most accurate range of sharp to soft edges. You get a little bit overly crisp at times and it is affecting the focal areas a little bit. Watch those edges!
My only comment at this point is to begin experimenting with the textured brushes so that you capture surface and edge qualities more accurately. Values and shapes are looking awesome...edges and atmosphere will improve with the texture and surface work.