Wow! I wish my first sprites looked like this! Very good job.
Some things to note:
1. When you're doing an idle stance look for parts that seem "glued" or stuck. It looks as if the sprite is doing shrugs. You should try to incorporate more motion if possible. Adding in some "sway" could breath more life into the animation.
2. The same thing with the running animation, the shoulders and upper body appear motionless in terms of vertical movement.
I don't have too much time to find resources but look at the end of this video. Notice the full body movement?