Unwanted Safari desktop picture
I error, I command-clicked an image off google, of a recently purchased external storage drive ( to replace it's current desktop icon ). This saved as a desktop wallpaper image and I can't get rid of it. I'd much prefer the original desktop pictures rather than this obsidian monolith leering out at me! It doesn't show up in the Picture folder in Desktop/ScreenSaver preferences. Where is it and how can I delete it?
iMac, Mac OS X (10.7.2)