Kimiko Powers was a major collector of Pop Art including the work of Warhol himself.  In 1981, Warhol was asked to make an artwork as a fundraiser for a visual arts program at colorado State University. This stunning portrait, 'Kimiko', was the result.  Warhol took multiple photos of imiko with a polaroid camera, before choosing the one for the portrait.

In this recent interview, Kimiko talks about the relationship between artist and collector:  http://amview.japan.usembassy.gov/wordpress/american-pop-art