New Properties for Audio Files

I'd like to suggest two new properties for Audio Files in QDocumentGallery

• the ID3v2 Tag TIT1 "Content Group Description"
  in iTunes it's called "Grouping" ("Werk" in German) and many people use it to
  organise tracks within an album.
  (but, unfortunately, no mobile music player on earth would show it)

• second, a thumbnail image for Audio Files would be very helpful (per Album, or per Track)