welcome bouzolf! Some C+C for your dude:
1 - I would consider going with 6 frames instead of 4 at that size. I think you will find that you can achieve much smoother motion that way!
2 - Regardless of how many frames you use, there are a few things I would keep in mind as you work on this piece:
3 - watch out for distracting lines in the motion - such as the 45 degree line shared by the extreme frames of each arm,
4 - you might want to limit the head motion to a single pixel per frame, like back-moving-front-moving-back instead of back-front-back-front-back,
5 - Your animation will be easier to distinguish if you do not just copy-paste and recolor the extreme frames to make the back leg and back arm - this will cause some confusion once you start actually coloring and detailing your character. Basically, even though you have 4 frames, to the brain it look more like 2 or 3 - if you've only got 4 to use you really should make the most of them! variety is a great way to start.
6 - a good way to test if you have enough variety in the pose is if you can still read the motion even if its a one-color silhouette or a rough line drawing...ben2theedge's recent thread has a great example of how to approach roughing in an animation:
http://www.wayofthepixel.net/pixelation/index.php?topic=4599.msg57614#msg57614I hope that gives you some ideas for where to go! Again welcome, and good luck on your pixelated journey