I did the various base coats on the diorama base today. Here it is, masked off for the first application of color, which is black that went on to the back, bottom, and edges.
After I airbrushed everything, I touched up some edges by hand. There were a few spots where a color got where it wasn't supposed to be, even with the masking, and some places where the masking left unpainted spots. Here's the end result.
I'm quite pleased. Next will be doing the detail work on the floor and steps.
While I had the airbrush going, I also base coated the barbarian's base.
It still needs shading and highlights, and some brown on the areas that are meant to be earth rather than rock.