Sites for Free Images (Most of these do not require attribution, but always check websites for their rules about usage.)
Photos for Class
This site will automatically include citations for downloaded images, ensuring that proper credit is given.
The images on this site are free to use without attribution.
Images on this site may be used for free without attribution. (Read carefully, and avoid clicking on the ads.)
The images on this site may be used by teachers and students for projects in an educational setting. No attribution is required.