The following links and suggestions will help you find images of medieval art which are not in your textbook but which were used in lectures or give additional views of works of art which interest you.  All of them worked at the time I posted this page, but may become outdated.  Please inform me if you discover any that are not working.  Some of these are individual images, others are sites with many works and require further searching within the site.

Irish Art

Lindisfarne Gospels
Book of Kells
Book of Durrow
Ardagh Chalice