It hasn't started shooting yet, but the newest Marvel TV show did reveal a fair amount about what's in store for Agent Carter when they do. There are returning characters, new Marvel characters being added, and some villains from the USSR.
Agent Carter is going to the well of Captain America talent a fair amount, announcing that the Russo brothers, who directed The Winter Soldier, will be directing the second and third episodes of the series. And they're talking with Joe Johnston, who did such a good job with the period in Captain America: The First Avenger, to direct an episode, too.
The beginning of the Cold War is going to be a major part of the series, with showrunners Tara Butters and Michele Fazekas saying that some of the villains will be from the USSR and that "the baddies that we would like to use, some of them do exist in the Marvel universe."
A tidbit revealed when we talked to the writers Steve McFeely and Christopher Markus after the panel was that Edwin Jarvis, the original butler to Howard Stark, will be a character in Agent Carter. He'll be acting as a sort of Q figure, bringing Peggy Carter technology from Stark.
We also learned that the TV show does take place one year after the first Captain America, but not after the Agent Carter one-shot. It'll at least start in the period before the one-shot, explained McFeely:
We like that richness of not being respected by everyone else and, by the end of the one-shot, she won. We'd like to live there a little longer. So the easy answer is, and we reserve the right to change this, this all happens before the one-shot.
As for the other characters from the one-shot, they said we wouldn't see them. They did hint at the return of Howard Stark and Dum-Dum Dugan, saying that "All those people have agents."
Finally, while the show is playing in a time period that has no other Marvel project is inhabiting, there is one thing we already know from The Winter Soldier: We already know how Peggy's life ends up. Hayley Atwell said that this was a good thing for the character:
I think it's easier in the sense that I always hoped that Peggy had a fulfilling life and to know that she did and was able to have a family and live a very rich life before she dies just means that this is just a matter of filling in the gaps. How exciting can we make her life as a tribute to the woman she ends up becoming?
There's a lot that can go wrong with doing a period piece on primetime network television, but it certainly sounds like they're getting all the pieces in place they can to make it great.