actually the idea has been done before. the female artist (elizabeth baradini or something to that effect, i think) did an airbrushed painting of a gal riding a horse going away from the viewer with a chrome dildo sticking up in the back of her saddle.
i can't remember her name for sure, but she has done alot of illustrations for penthouse i believe. if not that, then playboy.
sorry i can't be more specific... i saw the picture nearly 20 years ago.
even further back, queen did a promotional stunt for their song fat bottom girls that features the line "get on your bikes and ride" wher about 8-10 topless models had a 10 speed race. there's a pic in in the back of some pre 1983 playboy magazine. (penthouse?)