Cheers lads. It is howerver not my idea, I saw it on Marc Noelander´s profile on facebook, that he does it from these bricks. And I love it - very easy to work with, it holds the screws for wiring the trees very well, details can be carved better than on styrofoam I would guess..now I have to find the right way to do the finish - so I will experiment with different paints in coming days.