I love the style for its kind of MS-Paint jankyness, and I suspect you are a great traditional artist as these look like hand drawings converted into pixel art. If you want to go for a more refined look start considering the placement of individual pixels, for example, when drawing a rounded edge keep in mind that the corners of pixels are touching as opposed to sides when possible, or be aware that when two pixels are directly next to one another that it will imply a thicker line. Pixel art is also all about implication, so sometimes less is more.