Recently I posted about different shadows on the Wall and something just occurred to me while I was discussing shadowbabies. Most people hate (and some people love) them, just because of how powerful they are. But if we look at the situation at the Wall and the parallels between Stannis/Jon, it seems like something "shadowy" is going to happen.

Stannis/Jon Snow's Shadows

Stannis/Mel use two shadowbabies to kill Renly/Cortnay Penrose, afterwards they stop as Mel explains to Davos:

"Is the brave Ser Onions so frightened of a passing shadow? Take heart, then. Shadows only live when given birth by light, and the king's fires burn so low I dare not draw off any more to make another son. It might well kill him."

Which is then mirrored at the Wall:

R'hllor was a jealous deity, ever hungry. So the new god devoured the corpse of the old, and cast gigantic shadows of Stannis and Melisandre upon the Wall, black against the ruddy red reflections on the ice. -ADWD, Jon III

and:

The pit fire was burning low, and the king's shadow on the Wall had shrunk to a quarter of its former height. Jon Snow could see his breath in the air. Cold, he thought, and getting colder. This mummer's show has gone on long enough. -ADWD, Jon III

So if we look at the next part of what Melisandre said to Davos:

Melisandre moved closer. "With another man, though . . . a man whose flames still burn hot and high . . . if you truly wish to serve your king's cause, come to my chamber one night. I could give you pleasure such as you have never known, and with your life-fire I could make . . ."

and use that same logic back at the Wall:

"I can show you." Melisandre draped one slender arm over Ghost, and the direwolf licked her face. "The Lord of Light in his wisdom made us male and female, two parts of a greater whole. In our joining there is power. Power to make life. Power to make light. Power to cast shadows."

"Shadows." The world seemed darker when he said it.

"Every man who walks the earth casts a shadow on the world. Some are thin and weak, others long and dark. You should look behind you, Lord Snow. The moon has kissed you and etched your shadow upon the ice twenty feet tall."

Jon glanced over his shoulder. The shadow was there, just as she had said, etched in moonlight against the Wall. -ADWD, Jon VI

and:

She was stronger at the Wall, stronger even than in Asshai. Her every word and gesture was more potent, and she could do things that she had never done before**. Such shadows as I bring forth here will be terrible, and no creature of the dark will stand before them**.

and then lastly:

They crossed the yard together, just the two of them. The snow fell all around them. She walked as close to Jon Snow as she dared, close enough to feel the mistrust pouring off him like a black fog. He does not love me, will never love me, but he will make use of me. Well and good. Melisandre had danced the same dance with Stannis Baratheon, back in the beginning. In truth, the young lord commander and her king had more in common than either one would ever be willing to admit. Stannis had been a younger son living in the shadow of his elder brother, just as Jon Snow, bastard-born, had always been eclipsed by his trueborn sibling, the fallen hero men had called the Young Wolf. Both men were unbelievers by nature, mistrustful, suspicious. The only gods they truly worshiped were honor and duty.

I am not sure how exactly it would fit in the story, apart from it just foreshadowing Jon's resurrection, but Mel's future allegiance (between Jon/Stannis) will be tested, as well as the fact that this situation parallels the Night King as well ("when he gave his seed to her, he gave his soul as well") so who knows. I go back and forth on whether I want another one, but I am confident that if GRRM includes another he will do it right and make it amazing. Obviously we can't take all quotes like this as foreshadowing, hell there are numerous Tyrion w/giant shadow quotes as well.

That said another one would not only fit the "rule of three", but would also add the final shadow to Patchface's chant:

" Clever bird, clever man, clever clever fool," said Patchface, jangling. "Oh, clever clever clever fool." He began to sing. "The shadows come to dance, my lord, dance my lord, dance my lord," he sang, hopping from one foot to the other and back again. "The shadows come to stay, my lord, stay my lord, stay my lord." He jerked his head with each word, the bells in his antlers sending up a clangor.

TLDR: There's a potential connection between Stannis and Jon's shadows on the Wall and Mel's quote about shadowbabies.