I used a combination a a few different techniques. Some came up more prominent in the final and some not. I just played around with some of my favorite photoshop techniques, blending in different ways and masking out parts that didn’t seem to fit.
I started with the original render. Did a wand selection of the highlight areas, made a copy, and set to screen (played with gaussian blur here to make it a bit softer and layer opacity).
Next added some RPC people and other cutout people I’ve got, used those as selection guides to apply a black/white gradient over the people, set that layer to overlay and then de-saturated the context behind the people a bit. Added a Stroke from the filters menu to outline the people.
To bring out some more complimentary colors and keep things warm, I applied a warming photo filter to the interior and a cooling photo filter to the exterior. Played with masks, density, and opacity till it felt right.
I used my wacom in combo with the art history brush to squiggle some of the hard edges in the geometry and also in the carpet patterns.
I added the white vignette effect around the edges, but kept that layer below my people layer to help create some depth (successful or not, you decide). The client here wanted to show this as a space where people interact, so I focused the attention on them more than I usually would have.
I then duplicated a later that was pre art-history brush pass, and applied a Photocopy filter to that layer to bring out some of the edges, then set that layer to multiply as to only bring out the black lines for the edges.
Cropping, people placement, & exterior scene were all tweaked, moved around, and added throughout the process. Also added some EZstars to the lights for the flare you see there.
As a final touch I usually add a smooth grain to everything on a duplicated later and set to around 70% opacity. I think it helps unify things.
Michael