It seems Musicbee is unable to set a unique album artwork per album relative to the tracks, and instead only grabs whatever artwork the first track uses. Not sure if it's classified as a bug, so please feel free to move this thread to the bug reporting forum if that is the case.
Take this as an example. Each of the 4 tracks has their own artwork. The album itself should have its own unique artwork which is a combination of the 4 tracks' artworks.
However, when each track has their own artwork embedded, Musicbee only displays track 1's artwork in the album view. It doesn't see the Cover.png.
Now, if I set the album artwork as the Cover.png within Musicbee's artwork editor tab, it will change all tracks' artwork to the Cover.png. I can technically change tracks 2-4 without affecting the album artwork, but once I change track 1, the album's artwork changes.
I have to instead use a dummy file which appears before track 1, and set that track's artwork to the Cover.png. I don't even have to embed it, since it just uses the Cover.png, so that's nice I guess.
However, this makes the album look ugly.
I'd really like to be able to choose a unique album artwork that's independent of the track artwork.