How I do it:

First, there’s one thing, and then add another thing, and now there’s the space in between the two things.
An object plus an object, and the space in between.
Each object may cast a shadow, so now there are five things: two objects, plus two shadows, and the space in between. There’s also the space all around the five things, so that’s at least six things, which is plenty to work with. Visual alliteration. 

Need more? 
How about a door, a window, a mirror, the night.
Above:  Sun, stars, planets and especially Saturn because of the rings and the shadows they cast. The aurora borealis (looking up, I saw that happen). 
Below:  Wind, rain, seeds, flowers, twigs, reflections. The rings in the cross section of a tree. More rings.
Curving forms:  A swan’s neck, a bird’s wing, a ship’s prow. 
Reflections:  On water, in a bowl of soup; reflections in a cat’s eye… I never forgot that.
Dichotomies:  Lightness and weight. Push and pull. Above and Below.
Way Below: Underneath the horse’s hoof.
My imagery exists here, between memory, imagination and daily life.