I have thought about this often. DH and I love castles! One thing we came up with was using a large coffee table book. There are usually several available in the bargin aisles of the major book stores. You could use the book as is, or take out the pages and have them enlarged to a suitable size at a copy/office place. The pictures have to be large to begin with however, or there will not be enough resolution for an enlargement, resulting in a blocky or grainy look.

If you slightly enlarge several buildings, post them on a board, you could have a whole kingdom background!

Nann