You can audition different designs. Get yourself some plastic that is good for Overhead projectors. (at least A3 size is good)
Bind the edges with a tape so that you know where the edges are.
Lay your plastic sheet over your quilt and use Overhead Projector pens to draw possible designs in the blocks of your quilt. If you don't like them, erase and try again. The tape helps to stop you useing your pen right on the edges and inadvertantly marking the quilt.
This isn't my original idea, I saw it somewhere on the net, but can't remember where.