You can easily change the on your Whatsapp backgrounds
Follow Steps of Wallpapers for WhatsApp Chat Background App
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>> Open Application
>> Click on "Chat Wallpapers" Button
>> Choose One Categories you want to like
>> Choose Background image you want and Download It! (Wallpaper will be stored in your phone gallery)
>> Close Application
>> Open WhatsApp Messenger App
>> Click on Settings Icon >> Chats >> Wallpaper >> Change >> My Photos
>> Select your wallpaper from your phone gallery (The same wallpaper will be applied to all chats.)
>> Boom!!! It's Done!