walk could use improvement especially feet and hands movement.
try removing that middle frame and retweening with 2 frames.
This time dont space the distances so evenly, instead have a slow-in and slow-out with a big jump in movement in between.
This should make a more natural motion.
also the feet shouldnt look the same at any point like do in ur middle frame where it looks like u just used the idle stand frame. remember one foor stays on the ground as it goes back and the other gets lifted as it comes forward, try to shade the legs accordingly to show the knee bend and maybe go a darker shade on the leg thats going back to really nail it home.
in general I think the arms and hands stick out a bit funny.
I dont know whats goin on with that animation at the bottom, is it supposed to be idle/breathing or something else?