tapping Creative Commons sources for outreach

Besides the treasure trove at archive.org there is a lot that is tagged with one of the versions of the CC license.

Flickr builds this into its search (advance search) options already, but now the ability to search is being launched for accessing all varieties of digital files quoting MakeUseOf.com on February 8, 2017:

Just One Percent of the Commons

The new CC Search is currently in beta, so Creative Commons is taking things slowly. At the time of writing, the new CC Search only covers around 10 million images, which is just one percent of the whole Creative Commons repository. The goal is to eventually cover the whole Commons.