I backed the Fate Core kickstarter a number of years ago and have followed the thoughts of various people who were involved with it, and this has led me to applying these two ideas to Savage Worlds.
The first thing is Fate Core’s bronze rule, sometimes referred to as the Fate Fractal, which states that pretty much anything in the game can be treated as a character. For example if the purpose of the session is to survive a storm, you could model the storm as a character with skills and stunts and have it interact with the players possibly attacking with lightning bolts or branches that it knocks out of trees. Hampering movement with wind, rain and mud, and causing the characters to get lost.
The other bit is based on a blog post by Ryan Macklin titled NPCs and Ad Hoc Skill Modes. In this article I was exposed to the concept that NPCs do not need to have the same skill lists as the PCs. So while PCs might have skills such as Fight, Sneak, Shooting, etc. an NPC might have skills such as guard or merchant where guard would cover any skill that a city guard, or a caravan guard might need (fighting, spot) and merchant would deal with any thing that a merchant would need to know (persuasion, knowledge trade, etc.).
If you put these two items together, you could build a Savage Worlds haunted house adventure where the house is as much the opponent as any individual ghost is. An example of this for Rippers Resurrected would be:
A large gothic manor at the edge of a bog, supposedly the most haunted house in Wales.
Attributes: Smarts d6, Spirit d8, Vigor d4.
Skills: Move objects d6, Posses Victim d4, Project Images d8.
Only harmed by magical attacks.
At this point you would just have to decide how the building can be defeated, possibly ritual exorcism, finding the anchor and destroying, or just destroying the whole building depending on the setting you are using, decide how much damage the house can do by throwing objects at people, and what the house wants to achieve.
So if the manor wants to brood in isolation and will try to scare off or kill all who try to stay, you just have to find a reason for the rippers to go to the manor and spend time there such as it is a potential site for their new lodge, at least after they have dealt with the haunting.