Please add DB cleanup functions so when the user deletes an album/track/artist the corresponding data that was downloaded to support this entry is removed from the DB.
The images folders are the main issues as they are large and are currently not removed when deletions occur.
You can do this manually,
I take it your wanting it be automated?
Does settings > library > clean up automatically compact the database afterwards, freeing empty space? Is any automatic database maintenance performed at all? Is it necessary?
This does not remove the images that have been downloaded/added, and they are the vast majority of space consumed.