Those are a good start for a character design. It can see lot of room for improvement though. The charcters which you had came up with all have the same basic feeling to them, The next time you wanna make up some Game sprites, Try and made some really cute, Some sexy, Some mean looking and some just plain strange. If you look at any video game out there, or for that matter Anime or manga, IN one story there can be Many diffrent looking characters. The best example I can come up with is Final Fantasy. I those games the character look all different and it brings a depth of realized to the game.