Your work is not bad but there is not a lot of it. If you want a serious critique you need to exhibit much more and in various styles. "Pixel art" itself is not a style so much as a medium so you should display other kinds of pixel art as well as other kinds of art generally -- don't limit your portfolio to pixel art.
Making an income from art in any context -- videogame related or not -- is a difficult thing to do so don't put the cart before the horse. Practice, etc.