If the following exist I wish I knew how to employ them, otherwise I wish they'd be implemented.
* The ability to dynamicly change an ImageStyle's Playtime in-game (for instance, tie it to a slider via OnChange="Parent.AnimatedStyle.Playtime=Value" — this works in UIBuilder, by the way, just not in-game)
* The ability to force an ImageStyle to jump to a specific frame and then resume playing as normal (for instance, force a jump to the first or last frame, although being able to jump to any frame would be useful)
* The ability to pause and resume an ImageStyle's play progress
This last one is probably an even bigger ordeal than the others, but I'll include it anyway.
* The ability to define per-frame playtimes instead of per-style playtimes
And last but not least, a big old "thank you" to all you hard-working UI programmers. Y'all have no idea how much time you've helped me kill at work.