Well, with that one gone I had an empty wall with already mounted wall bands for an Elfa shelf system. Those are wall bands left there from my former Tehachapi Summit layout (http://blog.lsvedberg.se/#home). Since I had brackets laying around as well, getting a new shelf up would not be problem.
But I started by attaching my old backdrop, used both on the Summit and Three Yards Yard layouts, as seen in the picture below. It needs a fresh coat of paint, but apart from that it was all ready to go.
Next I built the shelf itself. I wanted it to be light-weight and slender looking. What I did was to attach a frame of 8 mm x 67 mm (1/4" x 2 3/4") lumber around a layer of 50 mm (2") extruded foam. And that was it. A sturdy but where light shelf, placed on the brackets. Like this:
It is no problem to just lift it off the brackets and down to the cupboards below when I shall work on it, if I find its normal height to awkward.