They're the wrong size, to begin with.
Second, they're not transparent. Unless you can paint masterpieces with MS Paint, DO NOT USE IT. Use Paint.net or Gimp. They give you more options and allow you to create transparency.
Third, make sure you know that only people who have a face downloaded can see it in-game. If your faces aren't good, like these ones here, nobody will download them, and thus nobody will ever see them. Make sure you get a good quality face before releasing.