I've seen that, they lay a piece of vinyl over the quilt top & audition quilting designs they draw with markers. You don't need a big piece of vinyl, half yard or so. Since the markers are wipe off, you can reuse the vinyl over & over.
Keep in mind you don't actually quilt on the vinyl, you just lay it over your quilt top to get a sense of what the quilting design will look like. You still have to make the quilt top somehow.
Good Luck,
Cathy S/Willowwind