The discussion on Wikimedia Commons (note that “Wikimedia” is their “umbrella”, similar to our MetaBrainz) currently suggests that as long as an artist has an identifier in a non-user edited system (e.g., VIAF or ISNI), then they’re notable enough for inclusion in Wikidata, which would also make them notable enough to have freely licensed images stored in WM Commons:
https://commons.wikimedia.org/wiki/Commons:Village_pump#MetaBrainz_Foundation_.28MusicBrainz.29_and_COM:EDUSE
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