Ask a librarian if you need help finding a citation, or if you are unsure of when to cite.
Google.com: (1) Search for your term, (2) Select Image Search, (3) Search Tools, (4), then Usage Rights. Choose a "Labeled for reuse" category that suits your needs.
Flickr.com: (1) Search for your term, (2) click License, (3) select Creative Commons only.
Clip Art sites from Makeuseof.com
The Public Domain Project (http://www.pond5.com/free)
video from Kimbel Library
College students often struggle with understanding how to use sources effectively and correctly.
Unless you're Darth Vader, make sure you're citing your sources.