This scene is LOADED with Clouds of various types and on various levels. The top sky is of course standard Horizontally Mapped clouds.

In FRONT of those is a Band of Clouds on a single
Vertically Mapped Plane. These were created with the
Flight Sim Cloud Set.

And in the Fore Ground are Procedural Clouds mapped
onto Vertical Camera Facing Billboards. I could have
added MORE Clouds to make it look even better- but this
is just an experimental render to further test my Cloud-Crazed theories.