i dont know exactly where this is going in your mind, but i leave a suggestion for you to consider..if i tap twice in a picture it zooms in..and if i tap twice again it zooms out..its perfectly logic and standard behaviour...but makes the "swipe up" redundant...i believe this gesture could invoke a serie of icons at the top for options like image rotation and slideshow..
once again thks for really nice work!

BTW..the "swipe down" to minimize wondow...sick, man..awsome!