You'd have to remember that one of the things that made RL medieval art a bit on the down side is the fall of Rome and its culture(and then the dark age with lots of bloody migrations etc), whereas in Westeros there's never been a great fall of a great culture.
Of course, Westeros is still a bit behind on some of the more sophisticated(and decadent?) peoples of the east.
Also, IIRC from school, the church in RL might've forbade or hindered depictions of realistic humans(of course nude, anatomically accurate statues woul'dve raised more than a shout), probably for reasons of anti-paganic worship and seperation from the "heretical" influences of Roman culture. There's been a "conflict" over that issue between the Catholic and Greek churches.
Of course I might be way off, it's been some time since school and I'm not too sure if the teachers had it right either.
