Here are a few ideas for this Halloween
Warhol, Picasso, and Lichtenstein artworks as Halloween Costumes
This site has a number of artist inspired costumes including a cool Gustav Klimt inspired costume
|Gustav Klimt, Adele Bloch-Bauer I, 1907|
A very cool one of Banksy's Love is in the Air (Flower Thrower) can be viewed here.
I found these cute kids costumes at Oh Happy Day.