To go with my palace diorama (see http://tidders-kingdomofwittenberg.blogspot.com/2009/04/grand-designs-7-palace-diorama.html) I also wanted to have some rooms to represent the interior of the palace. I looked round for suitable items to start from and eventually settled on using cardboard DVD and CD boxes. I bought one of each to make up some 'tryout' rooms; I removed one side of each box and put it aside for spare cardboard along with the lids.
The DVD box I have made into the palace entrance hall. The door porticos and the floor tile sheet are from a Dolls House supplier; columns are made from wooden dowel. The stairs are made from foam board and cardboard. The decor will not be pinky red when it is finished !
The CD box I made into a generic room (the door porticos and carpet are from a Dolls House supplier). The idea is to make sets of items to give different rooms - eg bookcases for a library.
Full decoration and fitting out of the rooms may take a while. I expect to finish the entrance hall first.