I just wanted to pop in with an update and let everyone know how the story turned out.
I contacted Pinterest and explained the situation to them. And they were very helpful. My tarot spread had been pinned to roughly 300 boards on that site, and it looks like Pinterest removed them all. Apparently, my little creation was very much in the copyright-able territory. Granted, Pinterest is a big site and the possibility exists that a stray image or two still remains. But I haven't found any lately.
It was great to see how efficient they were about it. It's good to know that people's intellectual property has value somewhere on the WWW (the Wild Wild Web), and that it's not OK to use other people's stuff however you want.
I also noticed that the form that Pinterest uses for people to report copyright infringement has changed. Shortly after I contacted them, the form got some options added to it. I actually wasn't able to use the form, because it didn't leave me room to explain that the infringement involved not the image, but only the text within the image. So I had to write an email explaining. Now the form has some extra options added, which allows people to be more specific. I don't know if the change happened because of my case, but the timing is interesting.
Anyway, my Haunted House spread has been removed from Pinterest. I wanna say thanks to everybody who came into this thread and offered ideas and advice.
It was all helpful, and it was great to hear other people's points of view and perspectives.