Does anyone know of a solution already created which would allow Album Artist artwork to be found and populated into an AlbumArt field (ID3, etc)? Not just “looking up” the artist as music is playing - the purpose is to populate the TAG on the media file.
Idea is: No desire for album-specific artwork, just a picture of the album artist.
Thanks. 
I have no fully ready solution for you, but fanart.tv and TheAudioDB.com are both services providing also artist images. At least they could be the sources for something like this.
Actually it would be cool if we would extend the existing plugins for Picard to also handle artist images. But for this Picard also has to learn about artist image as image type.
In this case, the OP wants to save the artist image as the coverart, so if the existing plugins could be set to download the artist image (based on the artist id?), wouldn’t that do it?
EDIT: I haven’t looked that code for the plugins in question or the api specs for the corresponding sites, so that may be a really stupid suggestion.
You are right. If the goal is really to show this instead of the cover art it likely would be best to save it with type “front cover” to the files. While this is semantically not correct it triggers players to use it for display.
So if this is how it should be the plugins could be adapted to that already. But one needs to look at their API, so far I had only looked in detail into how to query for release artwork.