Made some of these for christmas, turned out pretty well overall. I like the mc escher design engraved, turned out pretty well. I added in two ornate looking script words to put the peoples names in and scored that rather than engraving it.
they are mostly about 12 inches in width, the predgergast one was bigger, about 15-16 inches in diameter. Cherry one I made the board from two 8" s4s boards which makes it roughly 14" across. I did lose some of the wood cutting the circle.