Good for all your obsessive needs!

For people like myself who spend far too much time thinking about their characters and settings, I highly recommend Sweet Home 3D. It's entirely free, and you can use it to build rooms and homes and decorate them. It's relatively easy to use once you get the hang of it (though I say this as someone who has worked with 3D modelling programmes in the past), and gives you both a 2d floorplan and 3d view of your design. It helped me get my head around a flat outline I was trying to envision for a story. Plus, it's fun! There's lots of add on models at the website, and here (they need to be in Collada format [.dae], so not all of them are available), and you can import your own textures. If you have a few hours to kill and an obsessive need to house your characters, you might enjoy this programme.