Topless dancer during the minuet sequence; two other background characters have exposed breasts (one of whom has many) that are phony props, but the aforementioned dancer shows actual nipples.
Violence & Gore
None
Public Opinion threatens to use a whip, but never actually does.
Eros hits several characters with his arrows.
Alcohol, Drugs & Smoking
Mild
References to drinking alcohol. John Styx's breath revealed to be foul not from alcohol but from drinking of the River Lethe.