Wolfgang, thanks very much for that site! I didn't know about it, and it's FULL of really good pictures!
Jeroen, you might be interested in looking at
this thread on another forum. It has quite a lot of contemporary pictures of Franks from 800 and later.
You should also have a good look at
this site. It's FULL of Carolingian manuscripts, including the wonderful Golden Psalter of Saint Gallen.
Steven Lowe (otherwise known as Egfroth)