I just made a google search on Dresden plate images--was one with 20 petals. Also some with points. Robert Kaufmann has a free pattern that show you how to make the pointed version. You could adapt this to your size. I would think the points would be easier to manage than the rounded ends. If you prefer the rounded ends it won't take you much adapting to get your block the way you want it to look. Personally I think it looks pretty good right now!
http://www.robertkaufman.com/quiltin...dresden_plate/