When describing your PicBadge (either while creating a new one or while editing an existing one) set its privacy to 'Only me'. From that moment only you will be able to find and add it.
Bear in mind that if you add a private PicBadge to your picture (After all, PicBadges were meant for adding.. ) people would obviously be able to see the PicBadge on your picture. Nonetheless, You can make your pictures private too - Here’s how.
Please note also that if you set an existing PicBadge as private it might still be visible on pictures of people who have already added it before it became private.