If you've ever seen a picture of space, you'll most likely see that there is some kind of pretty nebula in the background. I would like to find out how I could create random, semi-realistic looking nebula, so my current background (gif below) looks less boring. The reason I want it to be random is because it wouldn't make much sense for the same nebula to appear over and over again. I've heard that shaders might be what I'm looking for, but I've never even touched a shader, so I wouldn't know.
What I currently have: