After I got them made and listed for sale, I thought about it some more (and thought about my soap purchase some more), and though "Hey, it'd be nice if soap sellers included a little face cloth with people's orders." What would be really nice would be if they bought them from me so that we could cross-promote a little. I started a thread in the Etsy forums, and was surprised at the number of responses I got. One of the first was from none other than HelloCrafty, from whom I'd ordered the soaps that inspired this.
I've also been contacted by over half a dozen more soapers. It looks like I posted that idea at exactly the right time, because a few have told me that they'll be finalizing their lines and packaging for the holidays in the next few weeks, and will order face cloths to coordinate with them. I really stumbled onto something here!
In the end, though, this is just another example of what I love about Etsy. Lots of people who do very different things, but eager to work together for everyone's benefit.