Hello Dick
Martin here - in fact your question is really about tagging.
In yesterday's software release I added some functions that refresh the tags in FLAC files. What that means is that if you add or change cover art or change the artist, album or track names - the new utilities will embedded that information in a tag in the FLAC file - mainly so that Sonos will sort the and present them nicely.
This is part of ongoing work there is a bit more work on FLAC and MP3 is next. MP3 tags are known as ID3. B2 will already display the images in downloaded MP3s but over the weeks ahead I will add the same functions now available for FLAC. When that's done - the images will become part of the MP3 file and will show on your car.
Its not a one time thing - you can change the image later and refresh the tags
Martin