You should try a little tip about MS Paint! You can go to properties and change the colours to black and white, and use the brush tool to have a little textured pixel brush, and then switch it back to colour to add some good colours! This piece is good but it does have the little white squares due to the texturing of the normal brush tool, the colours could be a little adjusted too, you should look up some colour theory stuff and learn how to make some awesome colour combos!