I shot this with my Nikon S9500 because the boys were moving and it was handy. (You know the old saying about the best camera being the one you have with you!) If my arithmetic is somewhat close (I'm not really certain about the sensor size so it's hard to be precise) the focal length was roughly equivalent to 550mm on a 35mm camera. This is difficult to hand-hold a lens this long under the best of circumstances, and that wasn't what I had here. Not to make excuses, but it was grayer than the processed image shows. With a more modern camera with more ISO flexibility and image stabilization, this would have resulted in a more conventional (read "less interesting") image. The fact that I knew the problems and shot anyway (pixels are cheap) makes this a serendipitous example of Semi-Intentional Camera Movement.
Hi Andrew, I'm guessing your exposure time wasn't that fast. What is interesting here is that your camera held two positions during the frame, hence the imprint of two scenes on the sensor.
This is actually one of the methods used in ICM, you should try experimenting with this.
Some ICM photographers start an image with an imprint, then move the camera quickly during the exposure to a totally different scene and hold to imprint. This then creates a blend of the two areas.
Definitely something to play with if you like experimenting on the creative side (takes LOTS of images as it is difficult to predict results).
P.S. - here's a 3 sec experimental shot I took recently which kind of shows the effect (camera held, then moved down during exposure then stopped to create a second imprint)