Clipart, ETC is an online service of Florida's educational technology clearinghouse. The Consumer Math section of the site has a number of illustrations that I have found useful to exhibit various types of commercial paper and indorsements. According to the licensing instructions, one may use up to 50 images per project, for educational purposes, without seeking permission. The site should be credited when images are used.
Credit for the following images: http://etc.usf.edu/clipart