Olof, given you mention Coverscout and this is a Mac forum, I assume you are using iTunes for Mac OSX?
If so, doesn't iTunes convert the WAV-formatted files to AAC or MP3?
Anyway, if Coverscout fails to find Cover information, you may try to install the following Apple script:
Search CD Universe for Album v1.0
Find Album Artwork with Google v2.5
Search SlothRadio for Artwork v1.1
They all work the same: You mark one of the tracks without covers, execute the script, the script will send a search string to the respective service, bring up the cover in Safari and you manually copy the picture to your tracks.
Kind regards, Stefan