If you have the pro version of Klwp you can save your wallpapers in the Menu(the three lines in the top left). This walls are stored in your phone in a fold named Kustom. Normally when you uninstall an app, the folders related to the app remain in your phone, but for more security, problably you can make a copy of this folder with an archive explorer like ES explorer and put it in other place of your phone.