I think its a bug, minor though. MB is pretty good at using the "folder.jpg" as the main image for an items thumbnail or poster.
Occasionally I may have to manually edit that, especially if I changed the ingredients of a movies folder contents.
This all works quite well, except for playlists. I would like to change the default image to something a little more meaningful. I go through the same process as I would for changing the image for any other media file. As you can see below, I've uploaded an image to represent this playlist and all looks and behaves as expected. However the image does not "stick", I still have the default image when I go back to the playlists page. This works just fine for everything else, just playlists are affected. Looks like a bug to me. Is anyone else getting this?