Hockney

This image was made by taking a ton of pictures of the same place from the same place and then putting them together. You'll notice that the biker with the yellow shirt is in their multiple times. (you may have to click on the picture to get a bigger image)
This picture plays off the same idea as the Hockney type image except that each picture used is see through to the picture below it. The background stays the same and becomes distinguishable, but the biker is in each picture and looks ghost like because the individual photos are semi-transparent.