I like your pictures if they leave room for my fantasy (or projection) like this one (and hides most of the treasures to be found) - personal taste. The model: perfect as always. Do you take the pictures as monochrome or turn them later into black/white?
Just desaturated? If I used simply desaturation before, the result was not that equally toned but some colors (like green in foreground and brown/dark red in background) melted into each other while others became more distinct. So I'm experimenting with the channel mixer in monochrome mode now. (Maybe it's not the scenery or processing tool but the lighting I should improve.)
.. certainly you must play around with the channel mixer, but you are right in saying that you have to start off with adequate lighting .. this shot is simply outdoors with an open doorway as a background ..
"simply outdoors" which leaves only a manifold of possibilities and given circumstances But I'll include this in my Scroll of Recommendations for the Courageous Student of Iconography. Thanks so far.
Long version: Time leads to sun ray angle which determines color temperature and shadow casting, clouds and similar atmospheric conditions cause scatter light in addition to straight shadow casting light, position of ray blocking objects, orientation of depicted area and camera...it'll take a thousand shots to train that intuition or instinct, to create such pictures without wasting too much of the model's time.