"Picasso"
A Vector Portrait of Pablo Picasso

Process:

I started with the preliminary sketch and the line art on a separate layer.

I added a gray background layer, hid the sketch layer and blocked in the black shadows on the line art layer.

Added a flat gray layer for the face and hat brim.

Added some crosshatching shadows

Added crosshatching on background.

Added mid-tone value to face.

Added more mid-tone values and highlights.

Final details added. Completed.

Close-up detail. If you look closely at the eye, you can see a miniature version of the portrait as the highlight on the iris.
Pablo Picasso Biography on Wikipedia: https://en.wikipedia.org/wiki/Pablo_Picasso