If you are doing hi-res (1x1) c64, you can only have 2 colours per 8x8 square (not including black). Low-res (2x1) is almost the same, only you get 1 more colour per 8x8 square.
Other than that, the white bg kinda sticks out too much, and the edges of his bubble have flaws, but I'm sure you were trying to figure a way make it looks right, so that's okay. Other than that, skills Ryu, this is an awesome piece.