Take a look at this computerized 9-patch generator from Levitated.net and see the zillions of ways a "simple" 9 patch can be created! You won't believe your eyes -- and it may just give you some inspiration for new quilt blocks.
After you've viewed the 9-patch blocks at the top of the page, hit your REFRESH button -- and a brand new set of blocks will appear.
The web page also offers this interesting information on the formulation behind the 9-patch block:
The basic building blocks of the nine block are limited to 16 unique geometric shapes. Each shape is allowed to rotate in 90 degree increments. Only 4 shapes are allowed in the center position to maintain radial symmetry.