Symbolism, Imagery, Allegory
Cletus collects pictures, which is weird, but not quite as weird as his love of potato chip bags. But his pictures represent more than a pre-teen boy's strange obsession—for Cletus, the pictures are important because they tell a story:
"Anything with a story to it" is what Cletus says he's looking for. (3.6)
As a kid from a small town, Cletus probably hasn't seen much of the world even though he's longing to see and do so much more. The pictures help him to escape his little town and see other parts of the world, give him space to make up outlandish stories to take his mind to other places and make him feel like the world is full of possibility.