When using MusicBee in full window mode, one pane labelled "Track Information" has an image that swaps between Album Cover and in my instance, Artist; being the two images embedded in each mp3 file.
If I switch to Mini Player when Track Information is displaying the 2nd image in the mp3, Artist in my case, then it is that 2nd image that is displayed in the Mini Player.
I would have expected the Mini Player to only display the 1st image in the media file, usually Album Cover, as the image in the Mini Player does not switch at interval.
Many times, I would start an album playing and then switch to Mini Player; and this aspect of displaying the 2nd image would not occur or be noticed.
Also, the image displayed switches to the 1st image when the next track starts.
My attention to this 'feature' only became apparent because of timing of the switch of modes and I have some albums with really long tracks.