Sigmar Polke

Sigmar Polke's works are often made up of multiple mediums and are multiple layers.

Edward Kienholz

Edward Kienholz recycles objects to make his artwork.

http://www.beatmuseum.org/kienholz/edkienholz.html

George Segal

George Segal is a pop art sculptor.  Most of his works are statues of people.

Shepard Fairey

Shepard Fairey started out with his "Obey" image of Andre the Giant.  He works with screen printing.  His most recent and famous work is the portrait he did of Obama with the word "Hope" written underneath.

Jasper Johns

Jasper Johns is an American painter and sculptor.  He started out doing window displays in New York City.  He is a pop artist and abstract impressionist.

http://www.jasperjohns.com/