To quote https://wiki.creativecommons.org/wiki/Marking_Works_Technical
Included Objects Objects included in web pages, such as images, should be annotated as above within their "host" web pages. Ideally all included objects should also embed object format native notice and metadata as described below, but this is only crucial for objects where the publisher intends for or is concerned about distribution outside the context of the "host" web page. Metadata about include objects that have their own URIs should be qualified with about, as rel="license" without an about attribute makes a statement about the current document (which is the "host" web page). Example:
Photo licensed under <a about="http://example.com/some-image.png" rel="license" href="https://creativecommons.org/licenses/by/4.0/">cc by 4.0</a>.
Perhaps this could be added to Commons as a mediawiki extension for Google to start picking it up and showing the licensing information in its search results. Currently Commons shows link tags with rel="license" attribute but they specify the whole page license, like they should.
-- Sveta