Prior to 200 Christians may have been constrained by their position as a persecuted group from producing durable works of art. Since Christianity was largely a religion of lower classes in this period, the lack of surviving art may reflect a lack of funds for patronage. The Old Testament restrictions against the production of graven (an idol or fetish carved in wood or stone) images may also have constrained Christians from producing art. It is also possible that Christians purchased art using pagan iconography, but gave it Christian meanings. If this happened, "Christian" art would not be immediately recognizable as such.
Early Christians used the same artistic media as the surrounding pagan culture. These media included fresco, mosaics, sculpture, and manuscript illumination. Early Christian art not only used Roman forms, it also used Roman styles. Late classical style included a proportional portrayal of the human body and impressionistic presentation of space. Late classical style is seen in early Christian frescos, such as those in the catacombs of Rome.
Early Christians adapted Roman motifs and gave new meanings to what had been pagan symbols. Among the motifs adopted were the peacock, grapevines, and the good shepherd. Early Christians also developed their own iconography, for example such symbols as the fish (ikhthus), were not borrowed from pagan iconography.
After about the year 200 Christian art must be broken into two periods: before and after the Edict of Milan in 313.
During the persecution of Christians under the Roman Empire, Christian art was necessarily and deliberately furtive and ambiguous, using imagery that was shared with pagan culture but had a special meaning for Christians. The earliest surviving Christian art comes from the late 2nd to early 4th centuries on the walls of Christian tombs in the catacombs of Rome, although from literary evidence there may well have been panel icons which, like almost all classical painting, have disappeared. Initially Jesus was represented indirectly by pictogram symbols such as the Ichthys (fish), peacock, Lamb of God, or an anchor (the Labarum or Chi-Rho was a later development). Later personified symbols were used, including Jonah, whose three days in the belly of the whale pre-figured the interval between Christ's death and Resurrection, Daniel in the lion's den, or Orpheus charming the animals. The image of "The Good Shepherd", a beardless youth in pastoral scenes collecting sheep, was the commonest of these images, and was probably not understood as a portrait of the historical Jesus.
The dove is a symbol of peace and purity. It can be found with a halo or celestial light. In one of the earliest known Trinitarian images, 'the Throne of God as a Trinitarian image' (a marble relief carved c. 400 CE in the collection of the Prussian Cultural Heritage Foundation), the dove represents the Spirit. It is flying above an empty throne representing God the Father, in the throne are a chlamys (cloak) and diadem representing the Son.
The fish is used as a symbol for Jesus Christ. It represents Jesus' last supper as well as water used to baptize Christians. In Greek, the word 'fish' provides the initials of the title "Jesus Christ Son of God Saviour" and was used as a rebus for Christ's name.
The lamb symbolizes Jesus' sacrifice or Christians when there are several.
The figure of the Good Shepherd resembles earlier shepherd figures in pagan Classical art that represent benevolence and philanthropy. Additional meaning would have been ascribed to the figure by early Christian viewers in the context of Christ's phrase "I am the shepherd: the good shepherd giveth his life for the sheep," and St John the Baptist's description of Christ as "the Lamb of God, which taketh away the sins of the world."
The Chi-Rho monogram, XP, apparently first used by Constantine I, consists of the first two characters of the name 'Christos' in Greek. It was popular in the period after Christianity emerged into the open.
The Cross symbolizes Jesus' crucifixion on a cross which was not represented explicitly for several centuries, possibly because crucifixion was a punishment meted out to common criminals.
Main article: Christianising the basilica in Basilica
In the 4th century, Christians were prepared to build larger and more handsome edifices for worship than the furtive meeting places they had been using. Architectural formulas for temples were unsuitable, not simply for their pagan associations, but because pagan cult and sacrifices occurred outdoors under the open sky in the sight of the gods, with the temple, housing the cult figures and the treasury, as a backdrop. The usable model at hand, when Emperor Constantine I wanted to memorialize his imperial piety, was the familiar conventional architecture of the basilicas. These had a center nave with one aisle at each side and an apse at one end: on this raised platform sat the bishop and priests.