Whenever I sync any song to my iPhone, some of the songs / albums display the wrong album art despite having the correct album-art in iTunes. I have had this issue since iOS 8 and all of my devices are up to date on the software side. Check out the examples below:
For example, Ride of the Valkyries shows album-art of ‘A Sky Full of Stars’ when I first synced to the device. After I deleted it from my iPhone and synced the song again, it showed album-art from ‘Songs from The Martian’. For the record, these albums are present in my iTunes library and they display it correctly. Be advised, this problem only with the album-art, not the song meta-data.
Hardware Info: iTunes 12.3 on Windows with iPhone 5 on iOS 9.0.2