I had to throw a last minute costume together for a party. After wracking my brain and scouring pinterest I realized the answer was obvious: Dia de los Muertos Calavera. Mexican Day of the Dead is full of colorful skull images dressed up as they were in life, so for this costume all you need is makeup. You really can wear any clothes you want.
I made myself a tissue paper flower and went with a dress and scarf for a little more traditional look, but I think it would be fun to add different twists. The make-up was $2 at Walmart and took me maybe 10 minutes to put on.