Dunno if it's intended, but when you select an album, then a track with the Artwork layout, the thumbnail browser only show the album artist of this album, while with the Album & Tracks layout, it still show the complete album artists list (the album artist of the selected track is just highlighted).
IMO, the thumbnail browser with the Artwork layout should work like it does with the Album and tracks layout. It's a lot easier to jump to another artist, while showing only one artist in the thumbnail browser is quiete useless. Highlighting the selected artist is enough.
just done for the main panel (i probably wont dont this for the library explorer unless there are a number of requests for that)
I'd really like to have the thumbnail brower for the library explorer. Would give more flexibility to MB layout:
Left panel & thumbnail browser side by side
Now playing & library explorer (thumbnail browser) stacked in left panel: