A couple of weeks ago I came across a post that suggested that a particular sort of bath mat could be used as a base for forests. At the weekend I was shopping at a local craft/homeware chain store when I came across a similar item. The material is heavy and would sit well on underlying terrain.
With a bit of colour work it shows definite promise forests for 6mm and is NZ$7 for a piece 80cm by 50 cm. I'm thinking about using it as a base for my WW2 winter terrain project. Painted black with a textured white spray paint it stand in well for a winter coniferous forrest.