Let's not forget that the first real idea of what the S8 will look like came from two leaked screen protectors as well, so those companies might really be getting first dibs on Galaxy S8 dummies or prototypes so that they can test their wares before launch, as there will be no flat version this time around, and curved glass is harder to make right. If that's the case, the design you see below must be pretty close to the actual retail units, at least in term of size and exterior elements.
We can clearly see the two iris scanning cameras on the right of the earpiece, then the front camera, light and proximity sensors, as well as the notification light on the left of it, and the SIM tray lid up top. There is one more opening at the top, which is probably the second mic, and the bottom houses the USB-C port, another microphone, and a speaker grill. The dedicated Bixby button on the left is visible, too, but the key takeaway here is that we are seeing the S8 and S8+ next to each other, and can grasp pretty well the size of these phones, which seems to be rather compact for their rumored 5.8" and 6.2" screen diagonals, curved flexible displays or not.