Finding free images can be time consuming.  Various museums in Australia have had open collections for quite a while and now the Getty joins the party.

“The Getty adopted the Open Content Program because we recognized the need to share images of works of art in an unrestricted manner, freely, so that all those who create or appreciate art—scholars, artists, art lovers, and entrepreneurs—will have greater access to high-quality digital images for their studies and projects. Art inspires us, and imagination and creativity lead to artistic expressions that expand knowledge and understanding. The Getty sincerely hopes that people will use the open content images for a wide range of activities and that they will share the fruits of their labors with others.”

http://www.getty.edu/about/opencontent.html