I have a number of artists in my local library where there is no thumbnail picture in the artists list but there is a picture in the artist’s page. Two examples are Diana Jones and Three Cane Whale. Adding a picture from the edit box does add the thumbnail but overwrites the artist picture.
These instances of missing artist images are going to become fewer and far between with the introduction of Art Director. You can find more information on this feature and learn how to contribute images of your favorite artists and bands with the link below!
The problem isn’t that there isn’t an artist photo, but that, in some cases, there isn’t what you refer to as an avatar in the linked article even when there is an artist photo, and there isn’t the option to add an avatar picture in the editor.
In other cases the avatar i a cropped version of the artist photo, which is what I would expect to happen.