Okay, I've added a few lightsources. Fires, braziers (though people seem to think they are treasure chests so they probably need redone), bowls of flaming oil and torches. Everything comes in a lit and unlit version. The zips are updated with the new additions so here's some screenshots of them in use:

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I also had a thought that I could probably put together a rough castle from the bits that I had. And so it turned out:
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I'm not entirely convinced by the lightsources yet. If anyone can lend some C&C I'd be very grateful.