Shadows create intrigue in any kind of artwork. Shadows on snow. Much more interesting than just snow.
(Okay, I'll admit the snow is cool, but there's actually a fair amount of shadow in that picture too. I have a hard time taking pictures without shadow, and I like keeping to the pictures that I've taken, if at all possible.)
I enjoy painting. I'm not that great at it, but I like to try. One of the things I learned in painting is that when you make a stroke of shadow under a focal point that really makes it pop. The shadows make the picture better.
It works in photography too, but you have to get your shadows in the composition (unless you're a pro at photoshop, like some people I know).
It is true for writing as well. We have to show contrasting characters and situations to make our Main Characters stand out. There has to be a conflict--something or someone to overcome (or be crushed by in a tragedy). Without the dark elements things are flat, like when there are no shadows in visual art. We need those elements to see our characters in three dimensions.
I've recently figured out that my darker elements (my bad guys) are not painting their shadows in enough. It's time to bring them out of the shadows, so to speak, and develop them more. Now's their time to shine. Mwa ha ha!
I'm wondering if the law of thirds applies in writing like it does in photography. In the sunset picture there are 2 parts light to 1 part dark. That is generally appealing to the eye. Is that how much darkness should be in our stories to keep them "balanced" (or maybe 2 parts dark and 1 part light, if you're telling a darker tale)? What do you think?