I have seen many large publishers use a slideshow where 1-3 ads refresh on every change of the slide. I can't seen to find any network that allows this, so looking for more information.
Worst case scenario, sell ads yourself. By doing slideshows this way you're going to be dramatically increasing your view count, which increases the price you can demand from customers. Try BuySellAds.com for a simple solution to selling ads on your site.