Most buildings only have two different arts, one assumedly for the Archaic and Classical ages, and one assumedly for the Heroic and Mythic ages. The Town Center appears to have a different art set for each age, and I believe houses might as well.
Greeks:
Egyptians: Norse: One thing I note about the Norse artset is that the Longhouse The only real conclusion I've managed to draw from this is that the Temple is a first age structure, which was strongly implied in many places anyway. Anyway, it was interesting and I thought I'd share.
TheShædøwDåwn
If you're like me, then it's possible you're a clone generated from my stolen DNA. I suggest you turn yourself in for destruction immediately.