MJ, I don't quilt, but do enjoy looking at the pictures of quilts and blocks. I think you will find that while the rounds may be a certain size, it is sometimes hard to tell where one ends and the next one begins. Since a lot of the Round Robin swaps cover many pages, it can be kind of overwhelming to go through some of the prior ones. In the last one Carriem put them in her albums
https://www.quiltingboard.com/member...04-albums.html I also found some other pictures of prior partially completed round robins pictures at
Round Robin 2012/2013 pictures
Round Robin 2012/2013 pictures
Round Robin 2012/2013 pictures
Round Robin 2012/2013 pictures
I'm sure there are many others that give some ideas of the variety of centers and borders. I've seen some of your BOOM blocks and enjoy seeing them.
Janey - Neat people never make the exciting discoveries I do.