well not going to be that harsh, but yeah this pretty much lacks a good amount of elements to be anywhere as good. you should check some tutorials about use of colors, shading, lineart, etc. so you'll give yourself a good  idea about where to start when aiming for pixel art. don't feel discouraged if this gets rejected, you can always ask for comments and feedback in the WIP section of the forums and someone evnetually will help and guide you on the right track.