Also, if you click on this.Ground in the Scene.setup, you will see the "Paint=" command set to the SurfaceAppearance that you selected. Click the Down Arrow, select "Import Image", and load a custom designed image.
Remember that this image will be repeated multiple times, so be careful that the edges match to some extent.
Try the quick .png file that I attached to see what it does to the ground. You should be able to right-click, and download it.
Have Fun