Loose that annoying and distracting background. The image looks very pixelated which makes the smothness of your blends hard to judge. Looks pretty good though.
Well, for a initial contact with highlighting it's fine. try using different colors for each part, so that in sharper edges the highlight is shinier and in those flatter as the forefoot use darker ones. Another good tip is to think aboit how the light hits the mini and just iluminate those parts which are capable of recieving light. appart from that the best way to improve is to paint, paint, paint