Good news -- everyone has received a center block!
And... the missing block finally arrived at my house, a few days after I posted all the photos. I've been mulling over whether to continue with the "surprise center" I had picked out, or switch to the "real" center, and finally decided to go with the real one. So here's a photo of it:
I already have a few ideas about a border for this one. Can't wait to see what you do with all the others!