Other than knowing that Peter Capaldi is the actor who’ll play him, we don’t know much about the Twelfth Doctor. Although we do have this recent hint direct from Steven Moffat:
“The Doctor’s always said he’s thousands of years old, and suddenly he’s going to look closer to what we know he secretly is. He’s going to look like an older man. A fiercer man. He won’t be the dashing young man he was a minute ago, and I think that’ll be rather exciting… [Peter Capaldi has] always looked like Doctor Who, how has this taken us so long?! Because the moment you say his name, you go ‘Of course!’ Because he’s got the hair, and he’s got the look, he’s brilliant, he’s known to be a fan, of course it’s bloody him!”
Toy manufacturers think that’s enough to go on and have already started in on his action figure. You can even pre-order the as-yet-unseen Twelfth Doctor action figure with delivery expected in May 2014.