If its really free try to get some galleryposter who will submit your galleries with your ads on it to TGP'S (Thumbnail Gallery Page) and MGP'S (Movie Gallery Page) you will get on this gallery sometimes over 1 million uniques a day.And if your product is free you can be sure many people will test it.

P.S if you want i can help you to setup thi stuff but you need to go online on ICQ