In the first centuries of its existence, the Church spread through a combination of empathy and kindness directed towards its persecutors and a focus on evangelizing within the major city centers. But the Church was not, nor is, a static thing. It’s alive and growing and, as such, it began to seek a creative outlet within not only the culture at large but also within itself. And so we begin to see the rise of an early Christian art.
Initially this art was primarily pictorial with a heavy emphasis on early Christian symbolism. The cross of Christ, the dove as a symbol of the Holy Spirit, olive branches as signs of peace, ships representing safe voyage through the storms of life, and the lyre as a symbol of joy all became standard Christian icons within art. By the third century the Church began to look outside of itself for new images and artistic expressions. Accordingly it began to co-opt the symbols and allegorical pictures from its pagan neighbors. Pagan imagery of Hermes and Apollo were transformed into images of Jesus Christ as the Good Shepherd. Images of Psyche were adopted into symbols of immortality, and legendary musician Orpheus was transformed into a symbol of the one who would ultimately tame beasts and bring peace to the world – God.
Phillip Schaff comments on this appropriation of pagan imagery in his History of the Christian Church: From the 1st to 19th Century:
“Some writers have represented this primitive Christian art merely as pagan art in its decay, and even the Good Shepherd as a copy of Apollo or Hermes. But while the form is often an imitation, the spirit is altogether different, and the myths are understood as unconscious prophecies and types of Christian verities, as in the Sybylline books. The relation of Christian art to mythological art somewhat resembles the relation of biblical Greek to classical Greek. Christianity could not at once invent a new art any more than a new language, but it emancipated the old from the service of the idolatry and immorality, filled it with a deeper meaning, and consecrated it to a higher aim.” 
This extension and appropriation of pagan culture and art forms extended even into the design of church buildings. Traditionally pagan temples were small, round buildings that were intended to hold only the pagan priests and a small group of worshipers. Rather than adopt this form for its buildings, the Church turned to the architecture of the Roman legal system and adopted the basilica. These were open court buildings having a long, central main hall with two smaller side halls running parallel to it separated by a row of columns. The end of the hall was generally raised so that a judge could preside over cases and be seen and heard by all within the building. Churches adopted this building style because it was conducive to worship. All of the congregants could be within the confines of the building, see the priest or bishop, and partake of communion collectively.
What are we to make of this appropriation of pagan art? Christian historians and art scholars have generally considered it to be a case of “plundering the Egyptians” –the taking of the riches and goods of the enemies of God and placing them in service to God. Just as the Israelites plundered the Egyptians on the way out of Egypt and put those goods to use in building the Tabernacle, so the early church took from pagan art forms such as statues, paintings, and even buildings and placed them in service to God.
This slow cumulative process of gentle conversion and appropriation and sanctification of cultural artifacts led to the longest period of Christian flourishing and cultural dominance the Church has ever known. For approximately 1,000 years from the end of the 5th century on, the Church would be the mediator and arbiter of what was to be considered true, good, and beautiful by the culture at large. It was a period of scientific, philosophical, and theological depth known as the Middle Ages, and it was not the dark period of repression that some would lead us to believe.
 Phillip Schaff, History of the Christian Church: From the 1st to the 19th Century, Vol. 2, Chap. 6, Sect. 79