Hi Skorium !
My explanations lacked details. Currently, I use Jellyfin only for music. I had already looked at the page you shared, but it seems to me (even if it remains a track) that it concerns mainly movies.
As for the music, there is on Jellyfin (and I use MusicBrainz for metadata and tags) two sections: a section “Artists” and a section “Album Artists”. For the “Artists” section, if the photos are missing, I put them myself. But for the section “Artists from the album”, as soon as you have albums with a group, an orchestra etc…the number of artists explode. And as I don’t plan to look for the guy’s photo who plays flute three minutes on an album…I’m looking for an image with a nice appearance for these future thousands of musicians who will not have their own photo.