When I'm out taking sports shots I'm always very trigger happy so I collect loads of images  and I've often wondered what to do with them. One day I saw an article about capturing astronomical images in a way that eliminated the star trails and yet enhanced the lack of light if you have to use a fast shutter speed. That started an experiment in using Photoshop to stack the discarded images and create a background for the better shots, these are the results so far.