Hi! this image: http://www.renderosity.com/mod/gallery/index.php?image_id=1643367&member
use a spotlight (with softshadows) just outside the window, directed inwards. Indirect lighting turned on and a big white wall on the opposite side of the spot (inside the room, not visible in this camera angle) for those photons to bounce from. A hdri for backdrop but not used for lighting, you can use an normal image for backdrop, work just as well. Hope this helps a little, but these kind of scenes are veeeery tricky to calibrate...took me several hours just to balance the light...