I’ve found another rich vein of book-holding Madonnas to use for headers. Apparently, it was specifically common in medieval times to draw a book over the belly of a pregnant picture of Our Lady. This brings new meaning to that whole “Mother of Wisdom” thing.
This header is from the “Madonna del Parto” by Taddeo Gaddi. He was a pupil of Giotto.
Raphael’s “La Donna Gravida” seems to allude to this old custom. (Unfortunately, you can barely see the book.)