I have been struggling with Cover Art naming for years and I would like to understand how the rules work better. I will summarize my understanding - correct me where I am wrong and I will update this post so it is accurate.
I prefer to embed the cover image in the music files, and capture all of the images in the folder for the album. Ideally, I would rely on CAA and local files for everything.
Cover Art Providers
The providers are searched in the order listed. The first providers that has any cover art is used and the provider search stops.
If you are trying to collect more than one image, the naming is important.
The key variables available for naming seem to be
%coverart_types%- multi-value collection of all types for an image
%coverart_maintype%- primary type for an image
%coverart_comment%- comment text with the image
In Options/Cover Art/Local Files, there is a regex for the local cover art files.
Here is the default (as shown in the image above)
First, non-capture group:
This is a non-capture group, so these will not get captured and the default (Front type) will apply.
For the second group:
This is the real capture, so if the names match any of the cover art types, they will be tagged as such.