Change security login background

I know how to alter the background for the login window that you see when booting, but I would like to know how to change the background of the plain black login screen that appears after waking a mac from sleep (when the 'require password when waking from sleep' security option is selected).

I would like to use one of the background images that come included with Mac osx or even change that black login screen to replicate the login screen shown when booting.

I hope I have made the difference between the two login windows I am talking about clear enough. I am just sick of that plain black login screen I have to see whenever I wake my mac.

(Using Snow Leopard)

Cheers.

I don't think there's any way to change the background in Snow Leopard. You should be able to do it in Lion...