After rolling through them, re-naming them sensibly (they were just numbers), compressing them for upload, doing a little cropping and so on, they were ready. Each Etsy listing allows you to use up to 5 photos. I like to use 4 or 5.
Then I went into the shop, opened one Rustic Wall Cross, hit Copy, and began listing all 8, one at a time.
This is great. I now have 15 of them in there, both large and small, and in lots of colors: lavender, blue, red, Aran Fleck, and more.
I'm a happy Etsy camper...