It looks genuinely excellent, one suggestion I have is that for the dark theme, you rerender the scene with darker colours instead of darkening the image, but apart from that I would actually see myself using this
So instead of just pulling down the brightness (which makes your design look drab), why don’t you make the dark version by changing the colours of the cloths to… you know… darker colours?
Hmm, what if instead of darkening the light you rotate it so it lights this from the side? I think the long shadows this would cause would be perfect for a dark version.