If you're using a walking foot, how about creating several sets of concentric squares or rectangles? You could start in the middle with one square, Stitch in the Ditch style, then make a square around that one, another around that, etc. then move to another area of the quilt and do the same thing. If you chose rectangles instead of squares, you could vary them by making some rectangles long and other ones wide.

Hope this gets her talking!