I visited the caves at Virtual Lascaux. The textures are gorgeous and the cave is interestingly maze-like, using torches to hint at the direction. It represented the chaotic, overlapping nature of the drawings well, but one thing it left out was the material imperfection.
In the real caves, the artists used the imperfections in the rock surfaces to hint at the bodies of animals - a bulge might become a shoulder, a gash might be an antler, or even color variations might be used to suggest modeling and features.
In the virtual caves, it was not that I thought the virtual rocks were not bumpy enough. It was more a question of what would imperfection be in this environment, and how could an artist use it to better effect? I suspect the answer probably has nothing to do with virtual rocks.