In my vision for the final battle in GoT, it will take place in the North. Jaime Lannister has deserted his sister and joins Jon Snow in the defense of Westeros from the Night King and his army of dead.
Unfortunately, with the swift destruction of ‘The Wall’, Jon Snow, Daenerys Targarian and their armies couldn’t reach Winterfell before the dead were upon the city. Arya and Sansa Stark managed to escape:
All life in the city has been wiped out, the only creature that remains is a white walker tasked with destroying the Weirwood tree that symbolizes Winterfell’s strength in the North, and resurrecting the remaining corpses. South of town city defenders tried to burn the bodies of fallen Northmen before they could be risen as wights, but they were quickly overrun and defeated. Note the ice that tells you were the white walkers and the Night King has touched the ground:
The armies of the living have retreated south to Moat Cailin, a strategic swampfort separating the North from the rest of Westeros. Here Daenerys and her army of unsullied are tasked with holding the army of the Night King back.
To the north the Night King and his army is approaching Moat Cailin. Using no special tactics and few siege weapons, he relies on strength of numbers and stealing the warriors of his enemies once they have fallen to lead him to victory. As several white walkers and thousands of troops have been sent to the east and the west to conquer the rest of the North, this is the only chance for the armies of the living to attain victory.
East of Moat Cailin, a hill fort resides in the mountains. It is from here Jon Snow, Jaime Lannister and Tormund Giantsbane will launch their surprise attack. With the aid from the Doth’raki and northmen, they will attack the Night Kings army from the rear while the siege of Moat Cailin is underway. The Doth’raki are of no use inside a castle during the siege anyway, they thrive on open fields as their wargrounds. The army have been given weaponry of dragonglass, and the goal is to take down the white walkers who control the wights, and ultimately take down the Night King in a swift one-ditch effort.
But to the east, an army looms unseen. Cersei Lannister and Euron Greyjoy have gathered the mercenary army of the Golden Company and transported them to Westeros. They reside in their base, waiting for the battle of Moat Cailin to weaken both armies. Once the battle is over, Cersei intends to pick up the pieces and destroy all that remains, the living or the dead. Equipped with valerian steel tipped arrows and swords, she is prepared to face whatever the aftermath of the battle of Moat Cailin throws at her.