The University of Arkansas Libraries Special Collections has a small but growing collection of artist-quality books of hours an other medieval manuscripts. The Libraries' Fine Arts Library also holds several excellent volumes with reproductions of painted manuscripts available to students. Several libraries and archives that hold complete or near-complete codices of medieval manuscripts have made digital surrogates available online. Here is a selection of some digital copies of manuscripts that Special Collections holds facsimiles editions of, along with other related works.
There are several sources of high quality digital facsimiles of painted and illuminated manuscripts. Some institutions provide digital access (partial or complete) to select holdings. Other organizations and consortiums provide virtual access to hundreds and thousands of manuscripts. Other special collections like at the University of Arkansas Libraries work with students and researchers to allow limited digitization of resources for research purposes.