The other day a short new HBO promo turned up on Twitter providing a brief view of a few Game of Thrones actors in season 7 costume. Today, HBO uploaded that video onto YouTube themselves, in HD, along with two other clips in the same promo series, and happily there are even more Game of Thrones actors visible in the lot now!
Along with shots of characters/actors that we saw in the first video such as Sophie Turner (Sansa), Kit Harington (Jon Snow) and Emilia Clarke (Daenerys), we now can see Maisie Williams (Arya) and several more actors in season 7 costuming.
The videos feature a long list of Game of Thrones stars: Lena Headey, Peter Dinklage, Kit Harington, Rory McCann, Nikolaj Coster-Waldau, Sophie Turner, Maisie Williams, Nathalie Emmanuel, Alfie Allen, Gwendoline Christie, Kristofer Hivju, Conleth Hill, Liam Cunningham, Isaac Hempstead Wright and Kristian Nairn (the late lamented Hodor *sniff*)
Source: Watchers on the Wall