Using found objects is one way to create a collage portrait. This is a collage reproduction of a very famous Vermeer Painting named Girl With The Pearl Earring. Below is the original Girl with a Pearl Earring (1665), considered a Vermeer masterpiece, Mauritshuis in Den Haag
This is an example of a different type of collage combining Pop Art with pattern on pattern. Chuck Sperry uses multiple patterns on top of one another and in combination with specialty papers. His work is silk screen.