Turns out that it's not easy to take pictures of my duvet cover. First, have to be sure nobody's under it (or on it- see below). Second, have to have the right light. Third, have to remember to bring camera to bedroom (not something I do on a regular basis!;) I'm very happy with how this project turned out.
To make it, I cut 12.5 inch squares from my favorite (triple-washed!) vintage sheets, and sewed them together. No quilting at all. I used a plain white sheet as the backing, and it's more or less a huge pillowcase. I did go back and reinforce the seams between the blocks with zig zag stitch, as this will be laundered quite a lot, and I don't want it to unravel.
ETA: I'm now offering vintage sheet fat quarters in my Etsy shop, if you'd like to do a similar project (dog not included :)