How to promote a charity auction at no cost? For example: www.ebay.com/childart?

As a charity organization the International Child Art Foundation must occasionally auction spectacular works by children to fund the Foundation's global arts programs such as the Arts Olympiad. This week we re-listed the works that did not sell two weeks back. Do you know what we should do to promote the auction? The art is great and the cause noble, but getting media attention or inspiring individuals to purchase art made by children seems impossible.