I looked through my architecture books, and the house that I came across that people might be most familiar with that came closest to resembling what the Old House looked like is Biltmore, located in Asheville, North Carolina:
The Old House wasn't anywhere near on the grand scale that Biltmore is, but it was all very much spires and pinnacles.
As for the pilot being shown again at the 40th Fest, I really hope it will be. I'd love to get the chance to see it again - and I'd especially like to see other fans get the opportunity to see it because it really should be seen by as many fans as possible. But according to Shadowgram Update #138's DS Fest "Hollywood Weekend" Report: "The 2004 DS pilot for the WB was shown in an exclusive one-time-only screening." I suppose all we can do is hope that something can and will be worked out to show it again...