Using Google Advanced Search
The Google search engine has an ‘advanced search’ that lets you search by ‘usage rights’ for content published to the Internet under an open license. The Advanced Search dialogue can be found under the Settings function or can be directly accessed at https://www.google.com/advanced_search
Image source: https://www.cccoer.org/learn/find-oer/
See Images & Videos tab for how to limit Google Image results by Usage Rights.