Well, here are a list of paramaters
1) Stars - Size, randomness of distrobution, desnsity, glow amount, etc.
2) Dust : You would choose up to 3-4 "layers of dust. Then you would set the color, transparency, smoothness, and maybe you would have some sort of curves like tool for changing the shape... Or maybe just a simple slider for the "curviness" of the dust clouds.