There is no cover art information in the XML from iTunes (just a line like this: <key>Artwork Count</key><integer>1</integer>). Normally we'd read the tags, but you don't have tags since you use WAV.
If you have the cover art saved externally, you could try right-click > Cover Art > Quick Find in File / Cover Art Directory...
Please share more information about your cover art saving system if you need more help.