@pony I don't know what formats those engines can process, but there is a whole cottage industry of interior modelling software and there are plenty of 3D models of various furniture. Maybe Unreal et al. can import such files too, or there might be a straightforward conversion for them, no clue. I needed some IKEA pieces before, but a lot of those models are for money.

Anyhow, my starting point advice is SweetHome3D program which can import standard formats. A good starting point listing a number of sites with 3D models of furniture is here: http://www.sweethome3d.com/importModels.jsp