I created this diorama using Sculpey back in 2005. As you can tell by the 28mm miniature standing inside it, this piece is fairly large
The various stone elements were textured with actual rocks when the clay was still unbaked, and then the additional cracks and designs were carved in once the clay was baked. All of these elements were put together and the flocked.
Here is a front view:
And a sketch of what I wanted it to look like:
Here are a few close ups showing the mini:
A detail of the dragon wings: