Trinity, after much playing with the albums which would not show the artwork I have finally solved the problem! All 9,000 songs on my ipod now appear in COMAND with the artwork.
This is what I did to solve the remaining albums that would not work.
1) Go into itunes and view all the albums as a list
2) From the menu bar click itunes>preferences
3) Click on 'Import Settings' and change them to MP3 encoder (192 kbits)
4) Highlight all the tracks on the album which does not work in COMAND. Right click 'convert to MP3'
5) The original version will still be highlighted when it has finished converting - delete these, leaving only the MP3 version on your PC.
6) Put itunes back in album cover view mode and right click on the album you just converted to MP3.
7) Go to 'get info', then 'yes' and then re-apply the artwork by clicking in the box and attaching the artwork
8) Sync ipod
9) Close itunes and copy the artist folder to your external drive
10) Plug into COMAND and update the cover art again
11) Plug your ipod into COMAND and disconnect the external drive. The artwork will be there!
I have some really obscure stuff and a combination of this approach coupled with your original answer and my previous post on 2 CD sets now shows all art. In fact, I had some albums where I could not find any art so attached photo's of the band which weren't perfectly square and they work as well using this method.
Please let me know if you have any problems.