From earliest times Christian iconography has likewise been a symbolic code, showing the faithful one thing and inviting them to see in it the figure of another. Some examples are: the dove, which figures the Holy Spirit; the fish, symbol of Christ, from the Greek icthus, an anagram for Jesus Christ, Son of God, Savior; the monkey or reptile as symbol of evil; and the bowl or pitcher of water and the vase of lilies that signify the Virgin’s purity in the Annunciation scene. In Christian art, form is thus the vehicle of spiritual meaning; in the expression and reading of this meaning lies the essence of Christian iconography.
The first Christian art was derived from "neutral images" which could be accepted by Christians or pagans.
These images included:
the Good Shepherd carrying his sheep (symbol of humanitarian concern)
the Orans (figure with hands uplifted in prayer)
dove (peace hereafter)
fish (Greek word "fish" formed an acrostic for "Jesus Christ Son of God Saviour)
Orans with two shepherds, one is milking a sheep, the other is bringing the lost sheep and the dog is watching him. The lanscape represents paradise on earth
The resurrection of Lazarus. Jesus is much bigger cos he's more important