Halving and doubling size
This method is similar to the continuation method, in that it uses images and can lead to interesting creative challenges.
I will imagine a scenario or look at a picture and change the size of one the objects in the picture. I will either double the size of the object of halve the size. Then I will pose the question "How can the object function exactly the same as before even though the size has doubled/halved?".
This would also be a good tool for brainstorming exercises (in groups). It has been widely documented how some folk can be inhibited in brainstorming sessions. With the halving/doubling size method the thought experiment (very much a lateral thinking provocation) is created automatically.
Halving the size of a ship's propellor: could lead to considerations of efficiency.
Halving the size of a TV's screen: I recently saw an idea for 360 degree television (the image would be viewable from any angle). The halving/doubling method could help to create challenges such as this.