How do you make the star backgrounds?

I'm writing a space shooter, now it's time for some bakground images, plain background and scrolling...How do you make¨the images with stars and nebulas?

Any cool program links?
/Tommy

depends on how the rest of the game is to play, ie One image or a really big backdrop. I personaly just get them from the Hubble photo libary.

http://gallery.artofgregmartin.com/tuts_arts/making_a_star_field.html