iTunes 12.5 - Add photo of artist / edit rainbow microphone thumbnail

No, missing artist images do not depend on the source of the music. Even if you bought it from Apple, you may get the ugly microphone images!

I don't have a solution, but I believe I've discovered the root cause of the issue.

In the iTunes store, each artist has a biography page. Some artists have a band image, others do not. For every artist in my library that has an image, it is the same image on their iTunes bio. For every microphone, the artists bio is text only.

It's true that the Artist picture (when iTunes actually posts it) comes from the artist's bio, but that doesn't mean it will show up. Take a look at these two photos. The one on the left side shows the microphone where Alice Cooper's photo should be. The one on the right shows Alice Cooper's bio page where there IS a photo in place.

It would be easier to look the other way if there was consistency. I'd just chalk it up as being a work in progress. That's just not the case. It's a bug that Apple has just ignored since the release of 12.5.