Instead of relying on Google or some other search engine to find resources for you, try this list of websites created by Professors for finding high-quality images.
Citing your sources properly -- yes, even the images you use! -- is important and required.
Purdue University's OWL Writing Lab Citation resources are the best ones out there on the web. Generally, Art and Art History courses require that you use either MLA or Chicago style. Detailed information on both styles are availble here.
Diane can help with citations, too!
