Wallpaper/Background Question

[burgler]

Hello, I'm running stock 2.1 on my Droid and I have a quick question regarding backgrounds.
I have a picture that is my homepage background that was taken with my Droid camera months ago. I set it as a background at that time (after cropping it a bit).
Then my SD card went wacky (it's happened a couple times) and I lost all the pictures I had taken with my camera.
However, my background image is still there, but I have no idea where the source file resides.
Could someone please tell me where the actual background file is once you assign one?
I'd like to test out new pictures for my backgrounds but don't want to lose my current picture if I want to switch back to it (it's a pic of my puppy...).
Thanks in advance.