Hi
What I do for darkvoid is generate random number of point stars, a few larger sprited stars all on a sphere, I distort the colour towards blue or red randomly too. Then I generate a few layers of 3D noise of various colours and merge the whole lot together. By priming the random number generator with a seed when I start the process I can guarantee that for the same seed I will get the same background. So I could use say, the sector names hash code to seed the rng.
Some backgrounds have no nebula type things, just stars, some have faint nebula, so are a mass of bright ones, it's quite fun sometimes to just sit there generating new backgrounds to see what falls out

.
If you run the darkvoid demo from the
website you'll be able to see the background for the 'first' sector.
HTH
Endolf