traffictrader perhaps? It's all template run. So basically you can set it up like this, (I think)
http://mysite.com/image.jpg runs template a
http://MyOtherSite.com/image.jpg runs template b
They both run through traffic trader, and can be updated every 15 minutes if you wish, or everyday, every other day, once a week... It's up to you.
Not so sure if it would scan. But you can set your file structure up to display "numbered images" and just have the templates run those numbers with each update. Traffic trader will automatically run those templates for you.
You could basically set up a years worth of updates, turn on traffic trader, and walk away.
