Question

In a work of art that is black, white, and gray, what would an artist do to the artwork to create emphasis?

Answer 1

composition becomes important. How is the work displayed, what is at the center or is one object bigger, too small are there lines in the artwork that point to the important object? The most famous painting would be Study in Grey and Black, aka Whistler's Mother, look how he creates emphasis.

Answer 2

contrast of values and composition( like dummysarefunny said!)