According to Pocketnow a Nokia Partner sent out a Christmas card with this picture of what at first glance looks like a Lumia 800, but then can be seen to clearly sport some give-away signs that something else is afoot.
The signs include the AT&T logo and what is clearly a front-facing camera.
The handset also sports the 4G logo, and the Lumia 900 is of course expected to be LTE enabled.
One can also see that the camera button is much higher, as can be seen in these other leaked renders from earlier indicating an overall larger device.
Read more of our Nokia Lumia 900 coverage here.