Resources for locating Creative Commons or public domain images. These are images that you don't have to pay for or ask permission to use.
Public domain works are no longer under copyright and are freely available to use. You don't need permission to use these images, but it's still good to include some attribution so others know where you found the image.
Creative Commons-licensed works are those where the creators retain copyright, but allow you to reuse them as long as you 1) attribute the creator, and 2) only use the images as allowed by the license. Some CC licenses don't allow you to reuse works for commercial purposes, or to modify the images. CC works often have logos like or , which tell you which license applies to that work. More about the CC licenses.
For citing Creative Common images:
Image title [with link] by Author [with link to their profile page if possible] licensed under [CC license with link].
Bottle of 100 anti-malarial pills, London, England, 1891-194 by Wellcome Images, licensed under CC-BY-4.0.
For citing public domain images:
Image title [with link] by Author, Date (if known, otherwise n.d.). Public Domain.
Cup of Coffee by Petr Kratochvil, n.d. Public Domain.