Album Art Solution !!!!!!
Here it is, could be due to many reasons, 5 mostly, found answers on this site.
I have the AVHP-8400BH and Im still working on all of this , but makes sense.
Im currently using the Mp3Tag, but also have itunes open, just so happens , that while following instructions on site below, Ive confirmed that the art work that are not showing are all with ID3v2.2,, and Itunes has a utility if you right click on a song or your entire collection to change the ID3 Tag to the reccomended ID3v 2.3
http://tips4pc.com/computer-gadgets/five-reasons-your-mp3-player-does