MrHotter
Explorer
I plan to make the primary antagonist the Death House itself(!) It is no longer just an inanimate structure but a cursed, malicious entity trapped within Strahd's demi-plane. For example,
* The party will hear regular (once/minute) but faint, low-frequency "thumping" sounds when the house is "at rest." When it gets "excited", however, the volume and frequency will increase to suggest a heartbeat.
* Should the party damage the house or objects (not creatures) within it, it will react in "pain" by slamming doors, blood seeping from the walls, shuddering from an impact, etc.
* The Death House fears fire and will actively attempt to extinguish an open flame, including candles and torches, and will react violently to fire-based attacks that affect it -- including attacks that miss their intended target.
* Any blood spilled on the ground or walls will be absorbed quickly.
* Footsteps of characters the house does not like will be amplified when attempting to move stealthily plus doors will creak loudly when opened and slam shut when passed through. Characters that openly respect the house will not be affected.
Sweet.
I also like the idea of footfalls sounding too loud when trying to be quiet. You can add to that by having the sneaky person hear two more steps after they stop moving.
I'm going to have the party hear a baby crying before they open the nursery and have it stop when they look into the crib.
I also want to have whispers from inside the kids room and if they put their ear to the door they can hear the kids saying how hungry they are but how they are afraid to anger their father by making noise.
I'm still deciding how they can find out about the affair with the nursemaid. I may have missed the clues in the adventure, but I think it's something I want to players to know about. Perhaps when they are in the main bedroom one of the male characters will hear a whisper in their ear "come to my room tonight, your wife will never know...". Then before they decide what to do with the swaddled baby she could whisper to the same person, "protect our baby from your wife...".