as somebody who is MUCH smarter than me pointed,
when I asked this question few years ago:
It is indeed a detail from Signorelli's "Hell" a fresco in the cathedral at Orvieto.
Scroll down here
http://blog.chosun.com/blog.log.view...&logId=1412079
The page is in Korean but the art is universal.
MUCH smarter than me because he was looking at the same avatar and this was all he had to give me answer.