Clouds

Try stuff like this:

a2234c542989671a70dddfe1d23924eb7842c8ac.jpeg

Bake to texture like this:
https://www.unrealengine.com/blog/getting-the-most-out-of-noise-in-ue4

Taking it to the advanced level:
http://shaderbits.com/blog/ray-marched-heightmaps