I think the initial post was asking about artistic elements, initially of functional significance, that are carried over into later periods when that original meaning has been lost. The most obvious example that
comes to mind are the X's and N's on
Byzantine coins like this one:
http://www.coryssa.org/2213431 which centuries before were used as denominational numerals but are here simply decorative. A more famous example would be the frilly shoulder gold strings as seen on the uniforms of stereotypical modern dictators which are a stylistic holdover of the
Roman pteruges (the
bit of leathery straps that usually is shown in "draped and
cuirassed" busts)
I don't know if there is a term as such. Maybe
art fixée or
skeuomorph?
