Earlier this year, there was speculation that Apple would use design cues from the Apple iPad Air for its next handset. There was even some talk that the model would be called the Apple iPhone Air and have a thickness of under 6mm. As a comparison, the Apple iPhone 5s is 7.6mm thick. Also, note that the corners of the device in the photograph are a little more curvy than the iPhone 5s, and there are white lines on the back that could mark a new placement of the antenna to the back of the device. While it is too hard to see clearly, it would appear that there are changes to the true tone flash on the back of the phone. Either it has been reconfigured, or replaced.
Also, on the back of the phone, on the bottom right, you can make out a sensor. Considering that Apple has been rumored to be working on some new health care features in iOS 8, including the rumored Healthbook, this could be a sensor that measures a user's heart rate, or some other important health metric. There is talk that the rumored Apple iWatch will take some health-related readings using built in sensors, and send the information to the Healthbook where it can be recorded and passed along to the appropriate doctors. It is possible that some of these sensors will also be available on the next-gen iPhone.
Once again, we need to bring up the possibility that these are not legitimate pictures. It is okay to be cynical and to take stories like this with a grain of salt, especially with a high profile device like the iPhone. We also have to consider that if legit, it could be an earlier design that has been passed on by Apple. But don't worry, this is just the beginning of what will no doubt be a long stretch of iPhone 6 related leaks that will keep coming until Apple unveils the device later this year.
source: Weibo via GforGames, SlashGear