Well I finally did find something to do with them, although I'm not sure why I didn't think of it before!
I recently bought these candles and candlesticks and thought they needed a little bling. So after a lot of unwinding and holes in my fingers from the wire, I got them undone and wrapped around the candles.
Now I just need to replace the tall candle with a real one (that's one of those fake battery ones) and I'll be good to go. I still have three napkin rings left - who knows where they will end up!