Finding images licensed for re-use has become easier. Here are some sites to explore:
Download the Open Access Button browser extension. When you find an article behind a paywall, click the open access button. The button will return a link to an open access version, if one exists, and also to any underlying datasets. If none exists, you can request a copy. Volunteers will contact the author and ask for an open access version.
Unpaywall maintains a database of over 48 million articles that can be published without cost to the reader. Similar to the Open Access Button, Unpaywall has a browser extension that can be turned on, triggering Unpaywall to automatically searches for free-full text PDFs versions of the articles you are looking for. Oftentimes, these articles are made open access by the author, in what is known as "Green Open Access." While these may not be the full, published version of an article, having access to pre-prints can be helpful in conducting research and forming a contemporary, topical argument on a subject.
