The final steps for added realism and mood were to use the Adjustment brush to paint a bit of brightness into the bottom left part of the window frame. This adds a bit more depth and realism. Lightroom CC was very helpful here as well, because I can now easily reposition brush effects by dragging the anchor pin, just as I can for Linear and Radial filters.
I also duplicated the lampshade radial filter in order to further brighten the light. I did adjust the values for that duplicate so that the shade was brighter, but not over exposed.
Adding some grain and a squarish vignette polished things off and gave me a more gritty, film-noir feel.