Lamp and sofa models from 3dsky.org PROFI collection
Picture on wall from DOGOSTORE
carpet patch model from Bertrand Benoit http://www.turbosquid.com/3d-models/fre ... del/587690
Parquet Floor was made with Floor Generator script.
I tested multiscatter for carpet and towel on sofa (or whatever

Carpet has 20000 instances
Towel has 500000 instances
I put one mesh emitter to window and 128 128 128 gray environment color.
2k image took about 1 hour .
other rush detail images about 3-10 min.
Here is 'before' and 'after' images;