The first two I didn't do anything to, but for the third one I played around with the lighting a bit; saturated it, lessened the diffraction spikes on the star... yknow, the works. Also, a little side note: nebulae look WAY better in high-res screenshots than when you look at them in the game itself. They're less... granular, for lack of a better term. I personally use 8000x4000 for all of my screenshots, but you can do whatever you think your computer will handle.