Is it possible, in theory, to give the Others a backstory in a way that does not ruin their mystique? Any backstory, not necessarily the show version.

I’d also add here Pratchett’s masterly prologue to said novel:

poorquentyn:

Sure! They’re an exaggerated omnicidal version of the Unseelie Court, aka the Bad Faeries, to the Children’s Seelie (or Summer) Court.

The faeries of the Seelie Court are rarely presented as an unambiguous good from the perspective of their human neighbors, and neither are the Children. The Unseelie Court and its various inhabitants, however, bring the true nightmares. They require no offense from humanity before attacking (check), they regularly abduct humans into their Horde (check), they enjoy toying with mortals and occasionally taking a particular one as pet (check), and they’ve been known to transform mortals into faeries (possible check). 

Of course, the Others are considerably more destabilizing to the overall cycles of nature than your traditional Bad Faeries, so one must also reckon with the enormous influence of Terry Pratchett, felt all over ASOIAF but especially in the echoes of Pratchett’s Elves in GRRM’s Others:

A land of ice…

Not winter, because that presumes an autumn and perhaps one day a spring. This is
a land of ice, not just a time of ice. 

And three figures on horseback, looking down the snow covered slope to a ring of
eight stones. From this side they look much bigger. 

You might watch the figures for some time before you realised what it was about
them that was strange-stranger, that is, than their clothing. The hot breath of their
horses hung in the freezing air. But the breath of the riders did not. 

“And this time,” said the figure in the centre, a woman in red, “there will be no
defeat. The land will welcome us. It must hate humans now.” 

“But there were witches,” said one of the other riders. “I remember the witches.”

“Once, yes,” said the woman. “But now…poor things, poor things. Scarce any
power in them at all. And suggestible. Pliant minds. I have crept about, my deary. I
have crept about o’nights. I know the witches they have now. Leave the witches to
me.“ 

"I remember the witches,” said the third rider insistently. “Minds like…like
metal." 

"Not anymore. I tell you, leave them to me.” The Queen smiled benevolently at the
stone circle.
“And then you can have them,” she said. “For me, I rather fancy a mortal husband.
A special mortal. A union of the worlds. To show them that this time we mean to
stay." 

"The King will not like that." 

"And when has that ever mattered?" 

"Never, lady." 

"The time is right, Lankin. The circles are opening. Soon we can return." 

The second rider leaned on the saddlehorn.
"And I can hunt again,” it said. “When? When?" 

"Soon,” said the Queen. “Soon." 

“Elves are wonderful. They provoke wonder.
Elves are marvellous. They cause marvels.
Elves are fantastic. They create fantasies.
Elves are glamorous. They project glamour.
Elves are enchanting. They weave enchantment.
Elves are terrific. They beget terror.
The thing about words is that meanings can twist just like a snake, and if you want to find snakes look for them behind words that have changed their meaning.
No one ever said elves are nice.
Elves are bad.”

Which I remember hitting me like a sledgehammer in the way it elegantly showed how so many of these accolades suggesting beauty, fame, and art have their roots in magical thinking and an instinctive terror of the nobility.