Make a couple blocks with your ideas concerning centers then lay them on folded fabric & play with the size until you have a ( pleasant to your eye) size background square. What you find pleasing will make the project more enjoyable. There is no set rule about size of blocks. After you make a couple plates you can determine what size blocks be determining what size quilt you want to make- then you will know how many plates you have to make. ( 12" plate on a 16" background square {2" on each side of plate} 5 across would be 75" wide, 6 down = 90" -- 30 plates. )
Adjust, determine by the size quilt you want & the size of the plates-- how many you want to make.
