How do I change the lockscreen background in Gnome 3 (Fedora 17)?

While seeking a solution to my login background question I realized that the lockscreen has to be configured seperately. But how? On a quick google search I only found the suggestion to replace the images in the Adwaita theme. Is there a better way?

edit /usr/share/backgrounds/beefy-miracle/default/beefy-miracle.xml,change the picture path which you set as below:

<!-- Wide 16:10 -->
<size width="1920" height="1200">/usr/share/backgrounds/beefy-miracle/default/wide/SundownDunes.jpg</size>
<!-- Standard 4:3 -->
<size width="2048" height="1536">/usr/share/backgrounds/beefy-miracle/default/standard/SundownDunes.jpg</size>
<!-- Normalish 5:4 -->
<size width="1280" height="1024">/usr/share/backgrounds/beefy-miracle/default/normalish/SundownDunes.jpg</size>

I did a straight replacement of existing images. I have performed other hacks to change the logon wallpaper, but I am guessing that this will also address the logon wallpaper.

Fedora 17 path is: /usr/share/backgrounds/beefy-miracle/default and from there you have /normalish; /standard; /wide and within each is beefy-miracle.png

i just found that in Fedora 20 (Gnome 3.10) they made a UI for changing the lockscreen background.

go to the settings, and open the background options, there are 2 choices one for the normal background and one for the lockscreen