Sam, Gilly & Little Sam
Westeros' favorite blended family made it to Winterfell last season after abandoning the Citadel and Sam's maester studies. The Slayer rightly deduced that everyone who could have been any help to him at Oldtown was far too out of touch to appreciate the urgency of the White Walker threat, so he stole some books and left with Gilly and Little Sam in tow. They eventually wound up at Winterfell (crossing the continent of Westeros with remarkably little incident) where Sam reunited with Bran years after the Night's Watch brother let Bran through the Wall beneath the Nightfort Castle. The youngest surviving Stark was much-changed when Sam met him again in "The Dragon and the Wolf," but despite Sam's minor shock and awe at Bran's new zen-like manner, the Maester-in-Training still managed to drop a serious knowledge bomb on the Three-Eyed Raven.
Bran calmly revealed that Jon wasn't his brother, but his cousin, and that since he'd been born a bastard in Dorne, his last name was Sand, not Snow. But upon hearing that news, Sam finally realized the significance of a wedding Gilly had mentioned a few episodes before in "Eastwatch." The meticulous High Septon Maynard had thoughtfully recorded nearly every detail of his life, including a very important annulment and marriage. When Sam here's about Jon's parentage, he realizes that not only is Rhaegar Targaryen Jon's father, he's his legitimate father, making Jon the rightful heir to the Iron Throne. How, when, and if Sam and Bran will let Jon in on this secret remains to be seen.
Jon and Sansa's respective right hand advisors are also on hand at Winterfell because, frankly, where else would they be? Davos traveled with Jon and Dany to King's Landing and presumably traveled back with them after the talks with Cersei ended. Davos' role remains a bit in question when it comes to Season 8 given that his arc has always been one of support. Will he simply continue to be a devoted servant to Jon or will some other brewing conflict steal his focus away from his duty. While Melisandre isn't pictured in this round of photos, the Red Woman will no doubt return to take care of her own unfinished business, and if the battle to against the Night King happens in the North, no decree from Jon Snow will keep her away. It could be there's one last confrontation to be had between Stannis' former advisors.
The Stark sisters' devoted servicewoman was another character revealed to be at Winterfell in the short clip we got showcasing Sansa's historic meet with Dany. Brienne looked on, noticeably worried at Sansa's greeting of the queen. The source of Brienne's consternation is unknown, but it's likely she doesn't buy Sansa's polite reception of the Queen for a minute. Despite their close relationship, Brienne's straightforward and honorable nature make her a horrible politician -- that's not to say she's ignorant or a bad judge of character. She's excellent at both of those things, but, as evidenced by nearly every photo of her, the Maid of Tarth is not great at hiding her emotions, and Sansa's had a history of shutting her out in the past. It could be that Brienne fears what she doesn't know i.e. what's going on in Sansa's head.
Or it could be her storyline doesn't revolve around Sansa at all this season...
When last we saw the Kingslayer, he was riding out of the capital as a light snow dusted the city for the first time in many years. He gave one cursory glance back at the Red Keep and his twin before turning his back on her and heading north to join the fight he promised he would. Jaime's always had his own sense of honor, however bent, and it was marvelous to finally see him break free of Cersei and follow it North to Winterfell. But what awaits him there? Dany might understand his assassination of his father, and even Jaime's attempted murder of her considering it took place in battle, but she likely won't trust him when he shows up without the army Cersei promised. He has value as a military strategist, but Dany has about 12 of those, so that's not likely to temper her rage when she learns of Cersei's betrayal.
Unlike many of the other photos that obviously show much of the cast at Winterfell, Jaime could be anywhere indoors between Kings Landing and the North. But, to be honest, it would be far more interesting should he turn up at Winterfell considering Brienne is there and so is Bran. The shove that launched the series happened at Winterfell seven long seasons ago, and arguably the moment that told fans exactly what kind of show they were watching long before The Red Wedding happened between those two characters. If they don't get some kind of reunion, can Jaime even complete a redemption arc? Nikolaj Coster-Waldau himself has said that's what he wants for Jaime. On Bran's side, he dealt with a trauma that he didn't remember and never got a resolution as to why his life was so drastically threatened.
He's moved far beyond incident as the Three-Eyed Raven, but if there's one thing we can glean from this batch of photos, it's that Game of Thrones Season 8 is returning to its roots. Pieces are moving into place making it seem like storylines that have stretched back to the beginning of the series -- including the White Walkers themselves -- are set to enter their final acts somewhere in the frozen North.