Hi Stephen,
Each 'cover art' image file is stored within its relevant 'Album' folder, along with the CD muisc tracks. The image file can be called any name provided it is a '.jpg' file. The Brennan just happens to name them 'coverart.jpg'.
The way the B2 seems to work is that when you call up a particular track to play, it searches the album folder for any '.jpg' file and uses the first one that it finds in that folder. This means that you can have multiple cover art items in any album folder (as I have with some of my albums).
So I have a good few 'Front.jpg' and 'Back.jpg' and 'CD.jpg' files in some of my album folders.
Like many others in this forum, I use NAS to access and edit the files and folders. It is so much more convenient.
Regards,
Peter.