Icons of the Theotokos
Theologically, the icons of the Theotokos represent the first human being who realized goal of the Incarnation: the deification of man. This is in contrast of the icons of Christ, the basis for all iconography, representing God who became man.
Number of types
The calendar of the Rusian Church, where iconography of the Virgin is highly developed, mentions 260 of her icons noted for meracles and celebrated liturgically. The Menaion of Sergius numbers the designations of Theotokos icons at 700.
The tradition attributes St. Luke with painting the first icons of the Theotokos. We know of three types he painted. "Umilenie" (Our Lady of Tenderness), "Hodigitria" (She who leads the way), and a third type, of her without a child.
Theology of the Icon by Leonid Ouspensky ISBN 0-88141-124-8