New answers tagged 2.2-froyo
Once you pick a wallpaper, Android actually caches it elsewhere. In Ice Cream Sandwich, Jellybean and Kitkat at least, try these two directories: /data/data/com.android.settings/files/ /data/system/users/0/ Inside one of those directories you should find a file called "wallpaper". This is a png formatted image, you may need to manually add the extension ...
Android doesn't save a history of old wallpapers. If the old wallpaper is still in your Gallery, just select it the same way you did before. If you've deleted it from wherever it originally came from (e.g. your camera photos or downloads folder), through Gallery or another app, then it's gone.
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