The Metropolitan Museum of Art has made a number of out-of-print publications available online (and free!) via their web site.
Among those that may be of interest to friends of the Belfry are these:
Sweet Herbs and Sundry Flowers: Medieval Gardens and the Gardens of The Cloisters by Tania Bayard
Textiles of Late Antiquity edited by Annemarie Stauffer
From Attila to Charlemagne: Arts of the Early Medieval Period in The Metropolitan Museum of Art edited by Katharine Reynolds Brown, Dafydd Kidd, and Charles T. Little
The Secular Spirit: Life and Art at the End of the Middle Ages
The St. Martin Embroideries by Margaret Freeman
The Unicorn Tapestries by Margaret Freeman. (I own this book and have found it immensely valuable, especially for its discussion of the plants and animals found in the tapestries)
Raqqa Revisited: Ceramics of Ayyubid Syria by Marilyn Jenkins-Madina
Peach Blossom Spring: Gardens and Flowers in Chinese Painting by Richard M. Barnhart
A Chinese Garden Court by Alfreda Murck and Wen Fong
And there is much, much more. Go plug in a few keywords and see what you find.