How can I use interior real estate photos (real ones) in connection with the 3D stager?

The better way to do that in Photoshop if you are not use 3d object. Not sure that Stager able to do that. 

Speaking from experience, if these clients are not looking at a million dollar listing, I would use my time much better elsewhere.  Clients know if a house is for them within 2 or 3 minutes. No video with a fake mockup is going to change their minds.  You are far better off to either hire somebody who does MatterPort, or - purchase the camera system, learn how to use it and go that route.  Trust me, the hours you invest fooling around in Stager would be better used finding future clients.  I can go to a photo shoot, spend 2 hours there taking photographs, and another 10 hours of creating amazing photograph finals for MLS and my portfolio.   If you work with homes that are in at least the 600K range, you put the work in, but I would never go the route you are thinking about, it just isn't cost effective. In the end, clients want to see *real* photos and go to the house in person. Where I live, rules are strict, I'm not even allowed removing a crack in a ceiling or wall. You are not allowed to change any physical defect in any building, as the realtor can then be at risk of repercussions from the purchaser.  Those are my thoughts on it.  ( P.S. I also base my thoughts on what a photographer is getting paid for a job, if you are getting paid 1K plus to photograph a house, and you have a lot of time on your hands, and want to do this as an experiment, that's great )  Most real estate photographers are shooting 4 houses a week, so are just too busy to anything more than composing final photosgraphs in Lightroom.