Images are selected to document each phase of a given manuscript's production, maximizing the amount of information available in a single image: thus, an image chosen primarily for its decorated initial may also supply visual information on the book's support, layout, ruling method, or quire signature as well as on significant divisions of a book's text. Explicitly chosen and signalled in the captions are production phases that involve shifts in script or decorative hierarchy, personnel, time, or place, evidence of ownership, bookseller codes and marks.

In recognition of the range of scholarly activity centered on medieval manuscripts, images in specific categories are also selected: for art history, usually all miniatures in a manuscript are photographed; for musicology, at least one sample of the musical notation is chosen; for book arts, if the book's binding is medieval, it is photographed, as are bindings said to be characteristic of a given library or collector, no matter what the date. On occasion, several leaves in sequence are chosen, so as to provide material for classroom use (e.g. an entire liturgical calendar; an entire poem). Most fragments are photographed in their entirety. All dated manuscripts are documented by photography and specifically flagged in the database, so that a searcher could restrict viewing to these images alone. Medieval documents are included for classroom use in the study of paleography and diplomatics.