This is an idea that I have toyed with on and off over the years -- using Cork to represent mountainous regions of the playing board. As a material, cork is a good one to work with. From a practical point of view, the material is very light and therefore can be transported with a minimum of fuss. Moreover, it is also "green" in the sense that it is regularly harvested and harvesting does not kill the cork plant. Its more like how sheep get sheared for their wool realistically.
To represent mountains, I decided to experiment a little bit with using different colours. On the example below, I have used Games Workshop's own white spray paint to coat this piece of cork.
I will say from the outset that this process uses a whole lot of spray paint to be honest! If you look closely at the image, you will also see that there are patches where it looks like I have missed my target when spraying. This is not true ... the cork absorbs a lot of the paint and some areas are a bit more resistant to spray paint than others.
What I will say though is that the overall effect -- certainly in terms of the texture -- looks impressive. The nooks and crannies combined with the layered visage of the cork makes this piece look very much like a small scale mountain or cliff.
I'm pleased with the overall effect here. Although I want to try more, I think that I might need to assess whether there's a better way to mass paint cork for a cheaper amount of money.