Even with the best of intentions you sometimes get really interesting images by accident. I apparently did not have the tripod head tightened down when I clicked the shutter. The camera drooped down during the 2.5 second exposure.
Which brings us to the point that when you have 2.6 seconds to play you can make some interesting images. Another possibility would be to zoom the lens during a long exposure. Always experiment, always be looking for the unexpected. There is no such thing a a mistake once the shutter button is pressed.
Equipment used for this image:
Shot at F16 2.6 seconds ISO 200.