Thanks to a tip from Susan Kitchens, I learned how to select pieces of terrains by what they look like. In the materials editor, SHIFT click on the name of the terrain and this window will pop up. Another advantage to this window is, that you can do the same thing with your own Deep Texture Editor gems and save them in the User folder for later uses.

Anyway, go through the list and pick a material that looks like it might make a good stained glass material.

I chose BlackWhite not for its colors but for its shapes. I clicked on the check mark to make my choice and then went into the Deep Textures Editor to modify my selection.

I added some colors (sticking with the reds and oranges I had selected for my sky) and altered the phase settings of the second component to give the material a different look than the original BlackWhite. To get to the Phase box, I clicked on the green spot on the top hand corner of the first phase box.

I then went back to the materials editor, increased the transparency, the refraction and the ambience of the material.

The resulting stained glass material you can see on the right.