The correct answer is: Traditional Roman and Greek art forms.
At the end of the 4th century AC, the Roman Empire was going through a deep political and economic crisis. The emperor Theodosius decided to divide the empire in two blocks and distribute them among his two sons. These two portions were the Western Roman Empire, with its capital in Rome, and the Eastern Roman Empire, with its capital in Byzantium, later called Constantinople. The Western Empire was strongly under the influence of the Roman culture and Latin language, while the Eastern Empire was ruled by a Greek elite, it had a strong Greek culture and Greek language was very extended.
What both empires had in common was their traditional art forms and culture. The Roman and Greek civilization were very similar since Roman took many elements from the Greek culture in the fields of religion, philosophy, politics, art, and architecture. These Greek and Roman roots shared by both empires were joined with the Jewish-Christian culture when Christianity was adopted as the official Roman religion, giving place to the cultural basis of the European continent.