How about getting a large piece of vinyl and placing it on top of the tablecloth. With a brown erasable marker (since that is what color thread you want to use) practice your design on the vinyl and you can not only see what it would look like but get you mind ready to FMQ. It can be a small section of the quilt or half, whatever helps you envision what you might want to use. Save the vinyl for the next project when done.