Who am I to not take a golden opportunity to whore my wares?
Use Content God
http://www.contentgod.com as your content management system. All you need to do is define one of the data fields for content provider for the images -- matter of fact, that data field comes as a default. Then you'll always be able to track all the images you use, where they are published, and where you got them from.
Content God -- The 2257 solution!
