Prominent tipster source @OnLeaks has a pretty good track record of providing accurate details of forthcoming devices, a lot of times this comes in the form of design details and schematics. In recent history it has made a habit of partnering up with other websites to bring forth 3D renders (in still and video form) of upcoming handsets based on said schematics, which, more often than not, prove to be fairly spot on to the final product.
The latest phone to get this treatment is the Samsung Galaxy S9 and Galaxy S9+, due for launch in early 2018 if persistent reports are any measure. @OnLeaks has teamed up with @91Mobiles to bring the Galaxy S9 render to life, and @mysmartprice for the Galaxy S9+, with both phones looking very similar as you might expect.
The Galaxy S9 is, of course, the smaller of the two (147.6 x 68.7 x 8.4mm) and looks very similar on the whole to the Galaxy S8. However, on the rear panel we can see it has a single camera sensor with a fingerprint scanner below it, arranged in a vertical strip.
On the front it's mostly curved Super AMOLED, and although it appears the top and bottom bezels may have shrunk a wee bit, the persistent rumours that the phone would shed a drastic amount of front bodywork to become 90% display appears to have been incorrect.
The Galaxy S9+ looks nearly identical except for the fact it is larger (157.7 x 73.8 x 8.5mm) and has a dual-sensor camera on the rear.
Both phones use the design style we've become accustomed to with a metal frame holding glass front and rear panels together, aka the "glass sandwich" now almost ubiquitous with high-end flagships.
The back panel appears to be more curved than the Galaxy S8 series, nearly matching the curvature of the display edges.
Both phones have 3.5mm headphone jacks and the Bixby button.