I want an image loading and caching library for iOS that
I had a look recently for the sort of thing you describe -- either a general data cache, or an image centric one -- and didn't find much of interest. So you may have to roll your own to get all those features.
There's a various blogs posts and things detailing such things, such as http://davidgolightly.blogspot.com/2009/02/asynchronous-image-caching-with-iphone.html.
I take it you've considered the Three20 library? I don't think it would cover your requirements though.