I am sorry for my English abilities because English is not my mother tongue. I hope you forgive me for mistakes I make.
I don't draw much so it took time to figure out how to draw. Especially how to start and not falling in to details. At work I overpaint or retouch, so i've never started with a blank sheet.
1.'Repose' - Sargent
For the first study I chose this one because here I was pleased by balance and economy. A lot of details in dress well balanced with left corner by table details and objects on and under the table And I wanted to practice in drawing folds. This one took about 4 hours. So after I draw basic shapes in first hour I've been carried away with folds and face for next 3.
2. 'Death dealer' - Frazetta
Here is a great example of emphasis. The black silhouette of the rider and the horse is outlined and set against a light sky. All figure is about death and power. At first all attention is drawn by the horse. So to pull attention to rider author made the highest contrast around riders head.
This one took 3 hours.
3. 'The Moon's Rapture' - Frazetta
At this one emphasis is made by frame of dark trees and light figure of the woman. The roots of the trees are also directed towards her. Observers look starts at the bottom of the painting then follows the roots curves to woman.
4. 'Retrato de juan pareja' - Velázquez
Here background is very simple, so nothing draw attention from the person. The area of most contrast is his collar and then the face. The portrait is very calm. It's not overloaded with details. I found out that it's hard to draw recognizable face at thumbnail size of paper, so i admit I had to zoom in to draw face details.