A work that is in the public domain is a work that is out of copyright and free to use. Works in the public domain may not need to be cited or given attribution, but the ethical thing to do is to cite and give attribution to another's work. "Information that is unrestricted and accessible by the general public - program which is in the public domain a program which is not copyrighted" - public domain. (2006). In P. H. Collin (Ed.), Dictionary of publishing and printing (3rd ed.). A&C Black. Credo Reference: http://libproxy.txstate.edu/login?url=https://search.credoreference.com/content/entry/acbpublishing/public_domain/0?institutionId=1143

See examples of work that are in the Public Domain that you can use at some of the cultural institutions and websites on the Openly Licensed & Copyrighted Creative Content For Your Scholarly Works guide

Getty Search Gateway or Getty Open Content Program

Public Domain Review

Picryl

Henri Rousseau's painting, "Jungle with Lion"

Jungle with Lion by Henri Rousseau, 1904 - 1910, is in the Public Domain