Lose or at least minimize the dithering on the old guy, scarecrow, and bald guy, it just add's noise and doesn't convey any real sense of texture or depth. It works alright on the sheep to make it look woolly, but is just busy on the others.
As for the animation, that is REALLY solid for a first attempt at animation, however you are right about the pony tail. The problem, in my mind, isnt the motion itself, but the way it synchs with the motion. Currently, you have the ponytail swinging up as the girl moves up. Realistically, it should swing downwards a bit as she moves up, and swing up as she falls downwards, so basically the opposite of how it currently is. The front tuft of hair, however, looks fine. Try and get some parallel motion between the two, it will make the movement look more natural and have some flow to it.