behind you ca directly view it. but some people also like to use a small one on one of the windows as well to alert any drivers on either of the sides of the infant in your car.
and then there are sassy and in-your-face types like these as well.
there are some that you can use your love for a particular show or movie.
it is completely up to you to remove these stickers after the kids have grown up but some people still keep them since they want to be surrounded by careful drivers at all times. 