All the castle needs now is some decoration.
I sometimes use icing left over from decorating the Christmas cake.
Fondant icing is good for sticking gingerbread men, trees and animals round the castle and in the courtyard.
I pipe icing on the walls, and it can be used to hide dodgy joints. You can stick sweets onto the walls, I use jelly tots as flowers, and chocolate buttons as roof tiles. A light dusting of icing sugar can pass for snow.
I've found the gingerbread castle will last for about a week. It is actually the caramel-glue which fails first as after a while it starts to go runny.