Gallery -> Displaying and Advertisement with Image

[pesci]

So I have popular image galleries on my site. The problem is that members can spend an hour browsing the photos without ever refreshing the ads. This isn't a good design. 

I would like to have an ad display along with each image impression. How would I go about including it? I toyed around with the code a bit, and I can get an ad to display, but then when the "next image" button is pushed a blank page loads. 

[pesci]

Any ideas? I need to monetize the gallery a bit better. Even just refreshing the entire page when clicking to another image would be better.