Wow! You guys are so amazing!!!!!! I don't know if your still taking theme suggestions or not but how about myth inspired ones? Be it Greek or Norse which ever you decide and that you've hopefully never done. Hope this helps and keep up the amazing work!
Hmm... this is giving me an idea for a set of chess keys. Not that I have the means nor ability to create such keys.
Though here's an interesting idea: a set based around the 7 deadly sins. No idea why, but the thought of a literal key that leads you to one of the circles of Hell just won't wriggle out of my mind. o.o
I love these colored roses you've been including on your latest keys. I'm planning on commissioning my own with a rose... when I have the money. How much longer will you have the materials to make them?