One more thing -
I was really pleased with how the Grass/Dirt turned out on the Top/Gound floors.
What I did was create a layer of Grass from a small patch (30x30 or so) taken from a screen shot. I then made another layer of Dirt in the same way. I took the eraser in brush mode, set the flow REALLY low, and deleted the portions of grass in the middle of the walking area. The result was very very close to the original.
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