As you know, GIFs are famous for animations. Such as this: But you know that GIFs aren't supported as background/WinterBoard theme files. Also, they don't support alpha transparency (Why some parts of an image are transparent), 24+bit color, and lossless compression. So, the absolute best (and my favorite) file format out there is the PNG. It supports EVERYTHING you need, and it's lossless at that too. BUT! The only downside is, it doesn't support animation. If you have Firefox installed, you should be able to see this image moving. If you don't use Firefox, then you should see a static ball: That's a special PNG format, aptly called Animated PNG. APNG's are FULLY backwards compatible with normal PNG's. That's why if you're not using an APNG-compatible browser, that image is still displayed. Now imagine, This is a full-blown PNG. With transparency support, and true color. This means you can finally have great animated wallpapers, themes, you name it, without a huge impact on battery life (as long as the image is not "Apple Optimized"). VWallpaper plays movie files as backgrounds; that hogs battery. PNG is already supported on the iPhone, and if that support is extended to be APNG compatible, then I can't begin to imagine all the possibilities. PLEASE tell me that there is a mod that enables APNG playback on iOS devices! If not, someone should make one; this is too good a file format to let it go to waste.