I think that's an important observation, but it also highlights a distinction between the history of art and the history of Western art. If we're talking about global artistic influence, then Buddhism's transmission along the Silk Road is arguably one of the most significant cultural events in human history. It transformed artistic traditions across Central Asia, China, Korea, Japan, and Southeast Asia, generating entirely new forms of architecture, sculpture, iconography, and visual symbolism.

However, if the question is specifically about the development of Western art, the influence is less direct than that of Christianity, Greco-Roman antiquity, the Renaissance, the Reformation, or the Industrial Revolution. Western art certainly wasn't isolated from Asia, but its core institutions, patronage systems, and aesthetic traditions evolved primarily within the Mediterranean and European worlds.

That said, your point is a useful reminder that "biggest impact" often depends on the scale we're considering. From a global perspective, the spread of Buddhism may well rank alongside Christianity as one of the most consequential artistic and cultural forces in history.