Your running animation is top notch and has a lot of character, but in comparisant something just seems a bit stiff about the relaxed state, arms out like he's carrying shopping bags chest out and an expression as if to say 'what are you looking at?'. I'd more really expect this character to have a more believable posture, I've made a rough edit of a suggest of what to do that's pretty easily done without going off on a tangent. I've not focused on every part and what I have done doesn't fix everything but it's a step in what I'd say is the right direction.
You seem to be shading for the sake of shading and not based on a fixed light source in places, too much shadow between the eyes yet no dropshadow from his hat. Other places too like the pick for example, theres no reason for it to be lit up so strongly, light wouldn't reach there so easily, plus darkening places with pixel art can push it back for our eyes making it easier for us to judge whats closer and further away. Mentioning that why don't you just use black? Its so close already and it really needs that extra depth. I'd avoid using extra shades too when you could be sharing colours, don't do it too extremely though because it can look too samely but some colours just aren't making too much of a noticable difference in this..
Again I've not fixed everything, well to say fix, I just think it could be improved on so much more.
