I would like some information on New York's laws regarding custom license plate frames. Does anyone know if they are legal or if they have special requirements?

Links to sites with information and more details about New York laws regarding vanity license plate frames or holders would be much appreciated.

StickyLife.com a company that provides customers with the ability to create their own custom license plates and license plate frames. We want to find out if our frames and plates are legal in New York so that we can better inform our customers.