It that possible for the wallpaper cache saved in Android /data folder being hacked? (Not Rooted)
If you'd like to be safe, you could always wipe the cache of the phone:


1. Turn off your Galaxy S3.
2. Hold down the Home and Volume Up keys.
3. Press and hold the Power button while still holding the other keys
4. As soon as you see the Samsung logo, release all keys/buttons.
5. Press on the Volume Down key to tab down to “wipe cache partition”
6. Once it is highlighted, press the Power button to select it.
7. On the next page, Press the Volume down button to highlight "yes" and press the
   Power button to select it.
8. Wait for a few seconds for the phone to clear the data.
9. Press the Power button on the next page to select “reboot system now.”
10.Wait for your phone to reboot.

  
  *This will not wipe any of your information stored on phone, pictures, video's, apps, contacts, etc. will all be safe


Source