A very slick surface that is easy to clean and wax, if necessary, so the quilt slides effortlessly. It should be white or light in color so it's easy to see loose pins, etc.
I have always wished for a 1" magnetic strip all the way around to catch pins, needle small scissors, and keep tails of my quilt from falling on the floor. The pins in the quilt sandwich would sort of catch on the magnetic strip. Just my idea of another pair of hands while quilting.