Open google search and choose random image. Look at the image for 10 seconds. Close your eyes and try to visualize the image. Be accurate regarding number and position of details. Remember as many details as possible. Try to visualize the entire image.
Combo of various fun images (Get pictures!)
Low level visualization: toy cars (Get car!)
Middle level visualization: optical illusions (Get illusion!)
High level visualization: fantastic landscapes (Get landscape!)