I put this together a looong time ago for a WIP that I never finished (
), so I'm making it available as a resource. I used a spectral map of Saturn's rings that I found online (this was in 2008, so I hope I'm remembering this correctly), duplicated it till I had a long bar. Then I used the polar coordinate distortion to curve the bar, and duplicated it to form a circle, after which I touched up the details to make it all look decent.
And now it's yours. If you use it, link back here so other people can use it as well, and I'd like to see what you've done with it.