Originally did this tutorial a LONG time ago, 5 or so years?
It was posted on sci-fi meshes while ago but guess it got wiped last year with the hiccups
3d Tutorials: Planetary Rings -1
Although made for Bryce and PaintSHopPro, it works with about any 2D app and any renderer that can load .obj models.
Includes a free ringed planet obj model (basic but it works!
), and texture file (.psd format, though you can use .png or make alpha maps)
It's not high tech, it's not MAX or Lightwave, but it works, and easily tweaked