This really is a lot simpler than you might think. The video below is a fantastic professional piece of speed art by a guy called Alex Koshelkov who has his own YouTube channel which can be found here.

All you have to do is to let your students watch the film below which is a good "watch" and at first you might think there is no way my students could do that in Photoshop!! However, I have run this exercise on several occasions now and you will be surprised what they can come up with. The piece of work below was created by one of my year 8s, You can compare the original with his effort to see what he achieved....

speed art - this is a big file of just under 90Mbt