As we teach our students to become digitally responsible, it becomes a struggle to find images that are usable under copyright law. I came across this amazing site on Twitter yesterday that will help to solve this problem. Icon Archive is an icon and image resource bank. All downloads are free and have creative commons licenses. The extent of each license is listed with the image. The quality of the images is really quite amazing.
The pictures below are examples of the quality that you can expect to find: