I tried to actually do the art on the window, but I guess the dust wasn't quite dark enough (or light enough) to provide the necessary contrast. So I did another version of the picture on the car's hood. I based the drawing off of a picture of a sea monster I found in a book. I did the window drawing with my finger and the hood drawing with water and a paint brush.

While painting on the hood, I got funny looks from people walking by, but nobody actually stopped to say anything...