The catacombs were used from the 2nd to the 4th centuries. By that time, all the writings that comprised the NT were written. What many scholars took to be central themes of Christianity from its earliest periods--the baptism in the Jordan, the sermon on the mount, the crucifixion and resurrection--are not depicted in the catacombs as far as I know. Rather Jesus is depicted as Hermes the Good Shepherd and as Orpheus playing his lyre and is equated with various figures from the Jewish Bible. Whether Roman Christians knew of these themes that dominate the NT or didn't accept them or accepted them but, for some reason, would not depict them is not known. But judging from Irenaeus' statements that Jesus survived the crucifixion and went to Asia to be a teacher which should have caused the Church to declare him a heretic instead of a Church Father would indicate that back in those days Christianity was very widely diverse and variant even within a single Church, sect or community.