Ao Shin is in Braum's background on champion page.

Look next to Braum's left shoulder, compare the eyes and shadowy figure to Ao Shin and you can see it.

http://gameinfo.na.leagueoflegends.com/en/game-info/champions/braum/

http://img2.wikia.nocookie.net/__cb20130908073927/leagueoflegends/images/5/57/AoShin_ConceptArt.jpg

EDIT: Pic for those who can't see: http://i.imgur.com/XRia2Bz.jpg

And regular splash art for comparison, it is not there! http://i.imgur.com/fqJUWqQ.jpg