piano room

i'd advice to set up ur own vraylight instead of using sketchup sun. the wall behind the camera.. put that in so u can control the illumination to come only thru the window.
the exterior.... the one behind the window.. try to use a picture that's more blown up.. brighter pictures. best that the details outside arent that visible.
about the flooring, introduce a displacement map or a bump map.. that'll add to the realism of the picture.
to get better results for renders...
smoothen out ur polygons, even the boxy surfaces. that'll add to the render time, but effects are good.
alternatively.. just post-process it in photoshop.
good try for a first!