I have done a similar project. Check out my still life #4 in my gallery. I did what EnglishBob suggested, and made the walls taller than the picture. No ceiling shows. Also, I left the walls that were not in the picture out. There are two spotlights outside the window offset a bit to spread the light out a bit once it's through the glass to simulate some ambience. I used a sneaky trick and put a modeled tree outside the window to get a throw pattern. I kept the shadow maps turned down around 200 I think to keep it from being too crisp. The rest are about seven spotlights shining into the room from the other side with very low shadow map settings. This softens all the shadows. In order not to wash out the window light, add spots with low intensities to slowly build up the light in your scene. I rendered probably 30 times. I noticed without a figure the rendering times were not too bad. I had zero luck with added ambience to the materials of the objects. They always glowed. Like others have said, there is nothing to do but test render alot to get what you want. At the end of it all, I still had to connect shadows to their casting objects in post. I kept getting a line of light along edges that should have been completely in shadow. Basically I post worked the shadow under the window sill and the left hand side of the curiorack. That's not very much post, but it would not have done for animation. Another thing to try, you can save your renders and not change the camera angle. If you wind up in the end liking different things in different versions, you can put them together in a paint program and use layers and opacity to fine tune your overall scene. Or use them as reference for final lighting. I don't like having to do that, but you might find a you can get a remarkably improved render by combining the images. In fact, most special effects lighting is not rendered in one pass at all, but a series of passes for highlights, general illumination, and so forth. I would like to see what you come up with in the end, if you would like to post it.