First off, thank you very much for the kind words. I'm am glad you joined the forum.
The "brown stuff" are in fact textured foam plates (roughly 37x13cm) which I bought from a train-modellism shop.
I know that the german company FALLER makes them, but there are certainly many others that sell similar products.
If you really desperately need those plates, amazon.de has what you need I think.
But I recommend you look for a train modellism shop near you, that will be cheaper
I hope that helps!