That's a lovely quilt. I see 3 different "blocks" for your custom quilting. I'd doing something that followed the "arrow" shapes (the light areas that point to the corners). Maybe adapt something from a table runner or a diamond pattern (I have a book of quilting designs that I use for inspiration, and that's often what I do - look for a similar shape and go from there). Then the crosses - I might even go with straight line quilting in the ditch on those, or maybe a cross-hatch. And the "circles" - dark center, light, dark rows. I see something loopy that radiates out from the center of those blocks.
Having said all that - I have a really hard time picking quilting designs. But I'm sure something will come to you, and the board members are really good at helping.