For the "micro-organisms" theme, I went with depicting the bacteria that makes yogurt possible: lactobacillus. In photo micrographs, it has a pretty basic cylindrical shape with rounded ends - like a pill capsule. I went for that look, and used the colors from the "spring" set.
I think this is pretty fun, and could even be mistaken for sprinkles. This came right smack dab in the middle of the results. My favorites were this very geometric one and this one with some interesting textures.