So here's a TV commercial for the Nokia Lumia 900 which popped up on youtube by youtube user: Feircejaguar.
The video features the sleek design of the Lumia 900 with the caption "Beautifully different"
Though this video wasn't uploaded by official Nokia, At&t or Microsoft channels, it looks legit and I assume it will be one of many Lumia 900 ads that will hit your TV starting April 8th.
As you are well aware the Lumia 900 is set to debut on April 8th and in stores the next day according to numerous sources.
and At&t also has put up a "coming soon" page for the Lumia 900 on their official website.
Check out the TV spot for Lumia 900: