Edited by Engelbert Kirschbaum.
Herder, 1968-1976. 8 volumes.
This work is similar to Reau's
Iconographie de l'art Chretien - but it is more a work of reference with longer bibliographies and lists of major works of art. The articles in volumes 1 to 4 consider the representation of particular biblical characters, events, and symbols. The articles in volumes 5 to 8 consider the representation of particular Christian saints, but with very little explanation. Many black-and-white illustrations.
Some volumes are available
online on the Internet Archive, a trusted source, but one for which it is necessary to create a free account and login.