What do you believe to be the actual and replicateable software bug here?
It looks like you have several artwork images that (besides perhaps their sizes or resolutions) show the same visual information.
(I'm not sure why you would want that in the first place to be honest)
Can you share the exact properties of each of the mage files you presented?
And explain what it is that you believe MusicBee is doing wrong in showing (a thumbnail of) each of them?
Sorry if I wasn't clear enough. The only reason I added two copies of the same image was to get proof for this thread. Both images are identical 1010x1010 JPG files, titles Cover.jpg (primary cover) and "Cover - Copy. jpg".
This is how said the primary cover (Cover.jpg) is displayed:
This is how said the alternate cover (Cover - Copy.jpg) is displayed:
I zoomed in on the screenshot so the differences would be more noticeable. Notice how the alternate cover shows more of the red border than the primary cover. I believe MB (in this particular view) slightly trims the borders of the primary cover while resizing/displaying it. I'm inclined to think this isn't intended behavior because it doesn't happen to alternate covers.