For those that didn't find the synth, it's here: http://photosynth.net/view.aspx?cid=5997f99a-60cd-48b9-a17e-148dccee2cb0
archaeosynth: First off, this is really, really cool. What holds the basement and living room together is the roman shade in the bay window. The texture on it is great for the synther. You need something just like this to link two rooms together - something with nice texture that can be seen from both rooms. The reason the rooms are not linked more strongly is that you only have one good shot of that shade from inside the room. (The second one is a little blurry)
As a general rule, you need 3 shots of anything to make it synth. Unfortunately it's probably been moved since you last took these photos, so to get it to connect more strongly, you'll need to re-shoot it from the basement and from the living room. Just add about 3 shots of that shade from the basement and 3 from the living room from similar angles and you should be set!