OK....lets go back and read the original post. I undrstand it must be quilted with the walking foot as Cowgirl does not do free motion. So that slets the style. With walking foot it must be straight lines or curves that you can manulipate with the walking foot (feathers and leaves unless very large would be difficult to do). If circles then they must be very large so the walking foot will travel around.
"Outside the Block", for me, eliminates SID or 1/4" outside the seam. Diagonals and squares are also out. If my spider web is weird then think about a block design that would cover the entire 40" square rather than individual blocks being quilted. A large single pin wheel pattern would meet this definitation in my opinion with lines along side it to cover the areas.
Straight lines from side to side forming a star would meet the requirements. Since there appears to be very specific instructions about how to quilt it (not design) then they should be followed.