This time, we have the official artwork!
Supernatural Wiki said, "At the Rising Con Spain 2010, Jensen and Jared confirmed the project and that they'd seen and approved the artwork for Sam and Dean. They also said they would voice the first couple of English language episodes."
Source: Comic Book Movie Fansites
Now Supernatural fans, you don't need to worry if they don't sound like them! About the artwork, it reminded me one episode that I watched in which Dean exclaimed this, "Do I look adorable?" Supernatural fan girls, what do you think?