The closer you crop the image, the more stylized the details become. It's common to want to include facets of the background in your stencil, but the closer you crop, the better your results are likely to be.
White powdered sugar on a simple, unfrosted chocolate cake makes a great combination. Use the lighter layer of a two-color stencil to make your design come alive. Works for sugar cookies too--just use the darker layer of a two-color stencil, and a dark sprinkle like colored sugar.