Ghost problem probably resolved
After investigation of some of my ghost-entries at "browse by coverart" I resolved the problem.
Cause: The file names of the coverarts in data/coverarts are generated using the ID3-tags of title and artist. If the tag values contain coincidentally double-blanks (0x2020) the double-blank in the corresponding file name is reduced to a single blank.
Consequence: The coverart can't be mapped to an entry in mpd database.