What is the best arrangement of lights to create a warm atmosphere in a small room?
To get a soft look, you can use:


lights pointed at the walls and ceiling, to reflect and diffuse the light
lights with a large surface area, like fluorescent tubes (which I use) or standard movie lights with big diffusers in front of them
lots of little lights, though these may create lots of little shadows


You'll still want at least a key light and a fill light -- that is, one light source that is the primary light source for your subjects, and another light source to one side that emphasizes that side of each actor (or object).

You can also add "warmth" in post production by color-correcting towards red or orange.