Hello! Your guy is pretty cute and there's nothing wrong with him, so I would start trying to push yourself to try some harder techniques. In particular, your animation is really simple- try making it more complicated. Here's the classic list of animation principles: http://en.wikipedia.org/wiki/12_basic_principles_of_animation Try making a jumping animation using the first principle, so he squashes a little bit when he lands, for example. To make it easier, try making parts of him different layers (like his legs) and moving them around if you haven't done that yet.
As an aside, the best way to resize pixel art is to use Nearest Neighbor interpolation, which can be found under the image size dialog box- but make sure you're sizing up by increments of 100%. So only do 200%, 300%, 1000%, and so on (not 150%), or you'll get weird differences in widths like the legs of your dude.
Keep at it!
Thank you for the tip and the link. I will be sure to try some harder techniques.