From Mark Tindall:

Some of the most erotic paintings have been with clad females images while naked female images have been amongst the most holy of paintings (like the Sistine Chapel).

A couple of links with easy explanations and paintings.

Nudity and Eroticism in Art http://www.students.sbc.edu/albanis03/psensem.htm

Sexuality in Art http://www.vergemag.com/0201/features/feat1.html