Last year Google released WebM as an alternative to h264 encoded video. They followed that up with the release of WebP as an alternative to JPG. Ever since the release I've been thinking about giving it a try on iOS to see how well it might work to reduce application size. As a bonus to reduced size, WebP also supports an alpha channel that JPG doesn't (there is more information available on the original release blog post).
Using WebP to Reduce Native iOS App Size