I think he's referring to the banners/tapestries. I'm not sure what to tell you except that the designs are ancient. It's interesting when you run across banners portraying ALMSIVI. Each saint has his or her own image too. Someone once pointed out a banner of Nerevar that seems to portray him after his death -- his body is apparently almost in half, and is a bonewalker.
Great House symbols are written in Daedric - a visual statement of separation from the warlords of the Aedra-worshipping Aldmer regions. The Imperial symbol is the Red Diamond - an Akaviri symbol from the reign of Versidue-Shae, in the Second Era.
Each Great House also has a pictorial symbol. Redoran has the Lorkhan scarab, Hlaalu has a set of scales, and Telvanni has their own swirly swirls and stuff.