That image, and the others in the gallery below, come courtesy of Zatz Not Funny, a tech blog that discovered the photos among the other listings on Anatel (.pdf). As you can see, it bears the familiar Amazon logo, a typical complement of buttons (including media controls), and a final button square in the center of the device that, as Engadget points out, resembles a monochrome take on the Amazon GameCircle logo. Specific tech specs on the controller are lacking, but we do know that it connects via Bluetooth and is powered by two AA batteries.
What the potential existence of this controller means is in question, but Engadget believes Amazon is "probably making a game console." Given the creation of Amazon Game Studios in 2012 and the company's recent acquisition of Killer Instinct developer Double Helix, that possibility may not be so far-fetched, though any such device is likely a long way off.