So my one suggestion would be on the 3rd board you make, have the road raise up. so it raises up, levels for a bit then slopes down again. That way it forms a bit of a hill, which if you put between those 2 you have now, stops therebeing a massive fire line the full width of the board right down the centre.
Otherwise, looks cracking! cant wait to see how the stair well looks.
Have you considered putting some posters on the buildings as well as the graffitti?