Over the camera would be a poor location for it. Aside from that anywhere should be fine, those stickers won't be able to block wifi/cellular/GPS antennas/radios in the iPhones design. If you are a really particular person goto ifixit.com and look at pics of your iPhone and try to put it over the battery as much as possible. Regardless the sticker isn't going to block anything more then the housing the phone is in to begin with.