The video gives us our first good glimpse at a number of new characters in costume and make-up (screencaps from Westeros.org):
Clive Russell as Ser Brynden 'the Blackfish' Tully, Catelyn's uncle.
Tobias Menzies as Ser Edmure Tully, Catelyn's younger brother and heir to Riverrun.
Nathalie Emmanuel as Missandei, a translator from Astapor.
Dame Diana Rigg as Lady Olenna Tyrell, the 'Queen of Thorns'.
Richard Dormer as Ser Beric Donarrion (replacing David Michael Scott, who played the character in one episode of Season 1).
Ellie Kendrick as Meera Reed, whose father was one of Ned Stark's oldest and closest friends.
Another shot of Meera, this time with her brother Jojen, played by Thomas Brodie-Sangster.
Looking pretty good so far. The promos also confirm that, after a lot of hand-wringing last season, Daenerys looks like she'll be kicking some backside this year. Also, what appears to be the set-up for a wedding or celebration. Interesting stuff.