Right, first of all I'll talk about the set I have been building.
The first thing I did, once I had the new measurements, was to make foam board walls to the correct scale. The scale was 50cm x 50cm x 55cm. These were then reinforced with wooden borders, knowing the foam board sometimes warps.
We decided that the easiest way to create the wooden texture of the cartoon, in our time-scale, was to do it with more shaped and carved foam board.
To then create a rougher texture, I then coated the set in "gunk" (Artex). The next thing to get done, is to spray it with a black paint, to give it a good undercoat for brown. I will most likely start with a dark brown, then dry-brush with a slightly lighter brown, then finally highlight with a lighter brown.