What can be traditional Art?
In the modern context of a certain type of art, "traditional art" refers to work on a physical canvas, something more tangible. The term itself is commonly found over the internet on art related sites to provide a differentiation from digital work. CG, or computer graphics, and other forms of digital media, have become a common enough media that a reference to the "traditional" is caused by the modern exploration of something that has not existed in the past.
This could work in multiple contexts, but there is a chance of "traditional art" being more than the common colloquial term as well. If so, historical artwork might be more suited to the term.