[pkscout]

Just a small feature request, is it possible to have the album art display instead of a blank screen as the fallback image? Quite a few of the artists in my music collection do not have available fanart because they're foreign artists. Instead of being left with a blank screen, I'd like to see the option to set the album artwork as a fallback maybe in the corner or centre of the screen?

Unfortunately, no. In order to show album art, AS would have to actually find and download it (I don't think there is any way to ask Kodi for the artwork). IT would be a substantial upgrade to have AS get album art. Depending on your skin, you might be able to bring up the On-screen Display (OSD) while music is playing. That usually has the album art and some basic info about the artist. That's what I do on Confluence. That way if there is no artwork I can still get some basic information about the artist.

Finally, what does "override slideshow"? do in the addon settings?

That allows you to designate a folder of images to show no matter what is playing. So perhaps you want to listen to some music and watch a slideshow of your last vacation. Pop the pictures in a folder, point the override option at that folder, and away you go.