I don't recall seeing this suggested before--forgive me if it's out there somewhere.
Cobwebs would be a fantastic decorating addition. They needn't be perfect-looking ones, either. Some that hang and some that could festoon the walls. What better way to make somewhere appear neglected and forgotten? Web-covered sdbs, a dusty chandelier...a corner web for the edge of a picture... Maybe this makes it too easy for us, but I'd love it anyway.