We also built most of our models from scratch.
A nice project I did once was - I used wooden dowels in constucting a log cabin.
Another place to get supplies and ideas is somewhere that carries a lot of doll house building & furnishing supplies. We would get sheets of shingle patterns, brick, stone, etc... and glue them to foam board.
If you have access to a table saw or band saw you can also cut your own dimensional lumber and all kinds of things from stock size lumber.