Using images and other media with a Creative Commons license allows the use of media without needing to obtain a separate copyright license.
"Creative Commons licenses give everyone from individual creators to large institutions a standardized way to grant the public permission to use their creative work under copyright law." from https://creativecommons.org/about/cclicenses/
Go to Google.com (or images.google.com) and search for the desired image.
Click Images [1].
Click Tools [2].
Click Usage Rights [3].
Select Creative Commons licenses [4].
The resulting images are covered under Creative Commons licenses.