Took an hour to render on gpu:
Very nice indeed! Congrats.
What is your graphic card, please?
EDIT: May be a lot of presence of the outdoor scene passtrought the windows…
It’s an AMD r9 390X. I rendered @2000 samples.
I tried with the denoiser and this can be rendered in half the time without noise if it can be used with the GPU. The beta builds can only use cpu 
Yeah the background should have been an alpha so you can put anything there but I just wanted to try it to see how far you can get with a few button pushes to create semi realistic lightning.
I also tried to render with light scattering but the graphics card gets to an halt for some reason. It only renders half the speed before it stops.
somehow the background trees are off to me. they are too dark and saturated to my eyes