You can always sell those as an expansion pack. It reduces nickel and diming and encourages game developers to create high quality content that they can actually sell as a proper expansion, as opposed to little bits that the user has to pay while in the middle of their game, often in order to achieve something that may barely be possible without spending that in app money in addition to what they've already spent.

But expansion packs are usually sold inside the game. The term in-app purchase is imprecise.