So far it is all told in subject. It is annoying if there are different pictures in the folder i.e. back.jpg that Subsonic will show that as a Cover picture.
I am using also Kodi as an Mediaserver, that will save a lots off pictures in the album folder.
So if there is no Cover in Meta-Tag there should be an option to ask for the name of the cover AND to disable it at all, if someone like it