I googled but didn't come up with much. Has there been any talk about whether Apple will allow third party developers to create and sell live wallpapers via the App store?
I also haven't heard about that the third party selling their live wallpapers in apple store. But if you want some exiting apps and wallpapers beyond apple store, you can jail break your iphone and explore it beyond the limits.
The only thing that I want to warn you is about using reliable software so that you don’t land up in trouble. There are countless applications that claim to jailbreak your device within a few minutes but not all of them are good. Before choosing any of them, do a little research and find out the customer reviews or feedback to know its utility.