In the Christian tradition, holy cards or prayer cards are small, devotional pictures for the use of the faithful that usually depict a religious scene or a saint in an image about the size of a playing card. The reverse typically contains a prayer, some of which promise an indulgence for its recitation.
A German holy card from around 1910 depicting the crucifixion
The earliest known woodcut, St Christopher, 1423, Buxheim, with hand-colouring
Prayer card of the Holy Face of Jesus
Prayer card of Our Lady of Solitude of Porta Vaga from the Philippines
Saint Christopher is venerated by several Christian denominations as a martyr killed in the reign of the 3rd-century Roman emperor Decius, or alternatively under the emperor Maximinus Daia. There appears to be confusion due to the similarity in names "Decius" and "Daia". Churches and monasteries were named after him by the 7th century.
St. Christopher Carrying the Christ Child, by Hieronymus Bosch (AD 1485)
Saint Christophorus carries the Jesus child, fresco in the Augsburg Cathedral
In Eastern icons, Saint Christopher is sometimes represented with the head of a dog.
St. Christopher, from the Westminster Psalter, c. 1250