The fields are (as torstan noted) simply a steel floor texture with some color adjustments and a bit of transparency The grass texture is actually the default overland filler for CC3, and I agree: it's simple and effective, I love it!

As for the scale, I honestly thought about it but decided against it. The problem really being that things really aren't enough to a real scale for my liking. My next version of this map should be to scale though.

Thanks!