Run Vensy Run

Here are a couple of things that could help you make this animation feel more natural. First, the legs don't bend at all. They just kind of rotate. With some styles of animation, this will work, but unfortunately, this isn't one of them. It's too detailed and has too much a feel of quality in the drawing style for such limited animation to fit in with it well. Similarly, as the legs move, the body should have a bit of squash and stretching going on. The back bone of canine/feline type creatures (I don't care if this isn't a real creature, there are some natural laws that have to be paid attention to if an animation is to look good) is flexible, so their body rarely stays a static shape. Also, an animal's head doesn't flop up and down with its shoulders as it runs. The motion of the shoulders will be dampened by the neck so that the head seems to have a graceful motion anticipating the rest of the body's motion.

Now, don't take my critiques too hard. I know animating with Photoshop isn't the easiest (it's what I'm using currently myself). However, since you do seem to enjoy animating so much, I thought I'd give you a bit of constructive criticism so you can have even more to enjoy.