Scott,
I think you're over thinking it. There are several painting techniques you can do to achieve the effect of light hitting a subject. Candle light, spot lights, moon light etc. But you have to take into account the context that the subject is viewed in. If you paint your figure to show reflected candle light and the highlights that result as well as the warm reflected light, it only makes sense if you add that candle. With a night scene, it becomes more difficult because by itself, standing out in a room that is well lit, there is no relative environment to help us correctly envsion the scene that puts the figure into context. A shadow box or box diorama can help but if you detract too much by closing it in and not add any light source (after all, all vision, night or day is dependent on reflected light off of an object)and take away from the figure, you "hide" your paint job. Where I have seen a 3 sided "stage" work is where it separates the figure from its universal environment (the exhibit room or living room) and contains it in its proposed environment (jungle, desert, CIC of a sub, alley etc). This becomes an aid for the viewer to see your figure in the context you intended.
As a side note, I have seen some very successful figures and vignettes painted in grey tones to replicate a black and white photo. This works if the figure is separated from external influences and is quite clever even if photographed in color. (In my opinion the only place this "trick" works is in a photograph) but......take away the thing that isolates it and it becomes less of an impact. Afterall, even black and white surfaces (or grey) will reflect the color light that is projected on it. So if I use a blue back surrounding or cool lights the greys and whites (and to some extent blacks) will reflect that color range. Warm those elements up into the yellow and red range and the same is true. Not being truly black and white. A novelty trick at best but IMO outside of a photo to truly trick the eye into believing its a black and white photo rather than color, it fails.
Accion Press publishes a series of figure books that are very nice overviews of sculpting, painting and reference. One in particular that deals specifically with this subject is the Monograph series Euro Modelismo; Painting:Overhead Lighting II that goes into information for painting lighting effects with acrylics.
Mike
"Imagination is the dye that colors our lives"
Marcus Aurellius
A good friend will come and bail you out of jail...but, a true friend will be sitting next to you saying, "Damn...that was fun!"