More not-really-random dots. Variable sizes, and some are stretched.
The number of different sizes are limited. The stretching is limited to the orthogonal directions. The larger sized items are more rare.
Initially the image seems rather busy. The additions generate more interest than just same sized dots. By limiting the addition to just a few patterns, there is a competing simplicity.
I made several of these, with various feature rules. More or fewer sizes, more or fewer orientations. I like this one the best. I also find it depends on my mood. Sometimes I like the simpler ones, sometime the more chaotic ones.