When the Christian cult came about it was ultimately consumed by the pagan world which ate it up quick and like napalm. The cult originally had been made up of Jewish radicals who believed in a man-god come to earth to fulfill the law and take punishment for the human race but these disciples soon realized that in order for this gospel to get off the ground it was going to have to be told to and believed by the rich gentiles who also happen to be their oppressors at the time. A lot of compromise took place to adjust the pagan gentiles to Christian life and as the old school Christian Jews died and the gentile converts took their place. Christianity became a intermingling of pagan habits and saving grace.
Elements in art that are pagan include personifications of nature, of attributes such as wisdom and victory, and even the halo which comes from the word Helios which is the name of a sun god. Almost all symbolism in Christian art from these catacombs, murals, etc. were pagan first. They were created by pagan converts for pagan converts who were both new to this cult. Why shouldn't they use for example this type of tree for that type of representation in the context of this Christian story so they both knew what they were talking about. The fact that Christian art was being developed in the first place is a pagan habit in itself. The second commandment states that man should not create graven images or idols. But it was the old passion for Greco-Roman classical sculpture that encouraged early converts like the city perfect Junius Basus to have a marble statuette of a seated Christ dressed in Roman attire on his sarcophagus. This pagan element however fused with Christian icon helped to market Christ to the pagans.
The only problem with so much pagan blending being allowed to take place is a spiritual one. Is the symbolism and personifications taking focus away from the true nature of God? Will pagan converts hold in high regard the marble idol itself rather the Savior it represents? And as time deludes oral tradition and translation of written word and the art is all that is left of what was wrote and said, what will be wrote and said then? What is wrote and said now?
For example. In early Christian art Mary the mother of Christ begins to be depicted often. Not so much in the beginning, but early on as more pagan influence interlocks with doctrine. Mary becomes an important part of Christian art, and the more she's depicted the more her titles become grandiose. She is even called Queen of heaven. The Christian cult sprang from what is called a patriarchal society who did believe there was one god and that one god was indeed a god and not a goddess. And they made it a point to separate themselves from the goddess worshiping pagans. It is possible that the glorification of the virgin Mary through art helped give her a demi-goddess status. As it did for other saints as well. They had different gods for different things. Now they had different saints for different things. the more things change the more stay the same.
So, the greatest advantage of this pagan blending for Christianity was the ease in which it allowed gentiles to convert yet keep in with some of their old tradition. (like not enforcing circumcision) Not only winning new believers but making friends out of enemies. And along with a few less people persecuting Christians there was now a lot more recruiting by way of art.
The only disadvantage is that the religion that the old school Jews met for it to be is long gone in the glorifications of murals, reliefs, icons, and catacombs. After the fall of Rome few for some reason were left that could read what these Jews had to say. So, they went by what they heard and learned from what they saw. And they were told what they had to be told so they would do what they were told. And they were being told by the descendants of pagan converts.