The only thing that would be left from any other owners would be the modernization of the house and things that they left when they left the house in a hurry, let's the just say that famlies didn't last long in the house. So if jessica wants to explore and find stuff left behind go for it, maybe even find some film from the 1840's when they filmed the experiments..maybe later in the story could cause some creepy tension, maybe old photo graphs of the patients......as for the wife of the doctor she would have been 23-24 when she died. She can be a ghost I would have her maybe reliving her last moments on earth every day....at a speicific time. As for any other spirits I waas just going to use them as noises or quick glances like running children