Towards the bottom of the Water Mill page is a link to the 'Window Construction'.  Below the link is a quick description of how I made them.  I'll be interested in seeing the pictures of your printing/plastic version.

I noticed that I forgot to respond to MattReid's balcony stonework question.  They were supposed to be the same green accent color as the other bits around the fireplaces and stone inlay on the various floors, but the wash was a bit heavy on the paint so the detail stonework turned out a bit too green.  I'll probably leave them until after I get the rest of the greenery put on the base to see how it looks then.  The wash also had no matte medium in it so the detail pieces are very shiny which doesn't help the look of them.  I'll certainly go over them again with some matte medium or some spray matte finish to knock off the shine.