Robert Wilken closes a superb chapter on early Christian art in his recent The First Thousand Years: A Global History of Christianity with a comment on the epochal significance of art in Christian history (pp. 53-4):

“‘A cultural event of some importance was taking place,’ wrote the art historian Paul Corby Finney,for we see here ‘a transition from models of accommodation and adaptation that were materially invisible to a new level of Christian identity that was palpable and visible.’ For the first time Christians were beginning to create a ‘material culture,’ something that is tangible, occupies space, is public (though underground), and is recognizably Christian. Art was an essential part of this endeavor.”

Wilken sums up: “The time was still far off when Christians could construct spacious buildings offering large panels for the display of Christian art. But the emergence of a Christian material culture in the early third century is a first step along that road.”

With that, Wilken highlights an underdeveloped aspect of ecclesiology.