Public Domain Resources

Public Domain image resources:

https://www.flickr.com/creativecommons/pdm-1.0/-- Images found through this search link (not the search bar at the top of the page, but rather the one under “Explore/Creative Commons”) on Flickr are in the public domain and are all free to use in any manner.
https://www.flickr.com/creativecommons/cc0-1.0/-- Images found through this search on Flickr have a public domain dedication (meaning that the copyright owner has waived his/her rights) and are all free to use in any manner.
https://search.creativecommons.org/-- The Creative Commons search is also helpful, but be aware that not all of the results have the appropriate licensing for your uses. After searching for your desired search term, use the filter on the left side of the screen to select only images that are “CC0” or “Public Domain Mark.”
https://pixabay.com -- Images on Pixabay are free to use without attribution in nearly any manner but are not within the public domain and instead bestow permission via a free license. Be sure to read the licensing agreement to understand what you can or cannot do.
https://unsplash.com/-- All images on Unsplash are free to use in nearly any manner but are not within the public domain and instead bestow permission via a free license. Be sure to read the licensing agreement to understand what you can or cannot do.
All records in the Open Content Program (Getty Museum) Open licenced images of collections in Getty Museum.(Make sure the box of "Open" in filter is checked)

https://www.loc.gov/film-and-videos/ -- The Library of Congress offers a wealth of culturally important videos via their online collection. Many of these recordings are in the public domain but be sure to read the “Rights & Access” information for each resource before reusing the work.
https://vimeo.com/creativecommons/cc0/ -- Vimeo has a collection of public domain dedicated (CC0) videos, which can be used without restriction. Be sure to click the small magnifying glass icon (under the “Creative Commons / Public Domain Dedication” heading at the top of the page) to search within this collection, as other collections on Vimeo may have different copyright status.