Somehow I came across the great clipart site, WP Clipart, which I have found incredibly useful. As it states on the front
page,
WPClipart is a collection of high-quality public domain images specifically tailored for use in word processors and optimized for printing on home/small office inkjet printers. There are thousands of color graphic clips as well as illustrations, photographs and black and white line art.
Except for a few “fair use” items — namely company logos (like the company name on a credit card) or recognizable products (like a particular model cell phone) — all the rest of the images are Public Domain.
There are many, many images in nicely categorized directories which are easily searched from a search box on each page.
