Thanks guys
Megacal the galaxy is a procedural used on the background node with a mask
that is made from a heavily postworked hurricane image i found on the web.
There is not much displacement-3D there. It is very subtle.
Probably an image as background would be the same. So nothing hard there.
Look at the file sharing section here.There are many good files to learn.
There is a file from moodflow
( Edit : http://www.planetside.co.uk/forums/index.php?topic=4391.msg46100#msg46100 ) .
You can used as it is or change it etc.
You can use the clouds as nebula's , galaxies too.