WhatsApp Wallpaper is an official application from WhatsApp that lets you place tons of predefined wallpapers behind your WhatsApp conversations.
To change the wallpaper of any conversation, you just need to be within the conversation itself and hit the menu button, selecting 'wallpaper' and choosing the image that you want. It's that simple.
WhatsApp Wallpaper is an excellent complement for users of WhatsApp, as it allows you to personalize your conversations with some very attractive backgrounds.