1. The Hound pointed out a mountain shaped like an arrowhead he'd seen in a fire-vision.
This was part of what drew the Hound north.
On the premiere of season seven, Beric and Thoros told the Hound to look into the flames. When he did, he saw a vision of a mountain where the dead were marching past.
Turns out we'd already seen that location before, back on the sixth season.
Here's the other side of that same mountain as seen by Bran in season six.
The Children of the Forest on the sixth season.
We saw this same location when Bran had a vision of the Children of the Forest creating the Night King, as Redditor Smurph269 pointed out. There was a rock formation in a spiral pattern — the pattern the White Walkers now often repeat.
It's interesting to think Jon and company might have been heading straight for an area beyond the Wall with immense ritualistic meaning. Perhaps the Night King even led them there on purpose somehow? Then again, it's also possible the "Game of Thrones" showrunners re-used a set in Iceland without realizing it.
2. When Jorah was trying to bolster Thoros' spirits, he mentioned a historic battle known to book readers.
Jorah Mormont and Thoros of Myr shared a nice final conversation.
Jorah and Thoros were both present at the Siege of Pyke — the final battle of Robert's Rebellion all those years ago. As Jorah said, Thoros was the first man through the walls, an act Jorah had taken for bravery but it turns out Thoros was black-out drunk.
That battle was where Jorah earned his knighthood, and it was also the fight in which Theon Greyjoy's father, Balon, was defeated yet again. At the battle's end, Balon was forced to give Theon to Ned Stark as a ward, setting in motion the eventual betrayal of Theon to the Stark family.
Though it was hard to see them, Jon's dream team was using newly created dragonglass weapons.
Tormund had a dragonglass axe.
What's interesting about the various daggers and axes wielded by our group of heroes is that previously it wasn't established that dragonglass kills wights. We knew it killed White Walkers, but there's a difference between the two.
However, in "Beyond the Wall" everyone from the Hound to Tormund was using dragonglass weapons against the horde of wights.