This isn't something I'm personally all that eager for, but I've seen other people mention it a few times so I figured I could at least make a ticket to add information to.

Sometimes artists feature in videos without actually performing in the song. While it's not all that relevant musically, I think it could still be considered information of interest (I know I would go watch/listen to a music video by an unknown artist if I knew an artist I liked was in it and I suspect a lot of other people would too).

I'm not sure what the best link phrases to use would be. I'm also not sure whether it should be limited to just people who would be in the database anyway or whether anyone who can be identified should be added. I imagine though that it would be more acceptable to more people if it were only for people already in the database.

The only examples I could think of off the top of my head are https://sayunii.wordpress.com/2010/08/17/smileage-onaji-jikyuu-de-hataraku-tomodachi-no-bijin-mama-preview-released/ and
http://www.jpopasia.com/news/new-akb48-mv-to-feature-former-members-atsuko-maeda-yuko-oshima-mariko-shinoda-and-itano-tomomi::17390.html