Changing image on lock screen on Macbook Air

Hi

When I turn on my Macbook Air. I have the older one with the USB jacks and the Magsafe charger the picture that comes up on the screen where I enter my password is different than my desktop beck round. I have the newest OS downloaded. I downloaded that a couple of weeks ago or after it came out. Is there a way to change the pic on the screen where I enter my password so it is the same as what is on my Desktop? Other than changing the Desktop picture to match.

Thank You