Unfortunately, I've chosen to remove XMBC due to this same issue. Too bad - I love XMBC aside of the strange way that cover art is read.
Frodo fixed a bunch of problems related to images on songs not being the same as images on albums etc.
I recently installed XBMC (prior to making my previous post) - Unfortunately, nothing seems to have changed (i.e. cover art not being read via mp3 tag).
Is there something I'm missing here? Thanks.
I've just tested it again. The problem seems to be fixed in Kodi 14.1 and above.
Thanks to whoever fixed it