My wife, from time to time, indulges in masturbation by taking two pillows, rolling them up, then straddles them, and begins to rub back and forth. When she told me about this when we first started dating I was very curious to see her perform this act. Although she was hesitant, she finally agreed. As her trust grew, she began to admit more. She stated she usually looks at softcore pictures of women when she rubbed on the pillows.
Sometimes I'll get a Playboy or Penthouse and watch her. While she's rubbing on the pillows, and turning the pages I'll lightly touch her anus or play with her nipples. She also has a HUGE fantasy of a man, or group of men watching her do this and masturbating themselves while she does.
Using my digital camera, I've taken a lot of pictures of her in the nude over the years. I'll tell her that I'm going to post the pictures in the Internet, and thousands of people all over the world will look at her while masturbating. She has the strongest orgasms when thinking of these fantasies.