I'm wondering if there has ever been a photo of Sparkles the Unicorn on Winter Bash.
Also, is there a particular reason that the Sparkles-related pages aren't formatted in Winter Bash style?
There have been multiple sighting of unicorns on the Winter Bash site, yet no one knows if any of those was meant to be "Sparkles".
Our tale probably starts back in 2013, when for the first time the Winter Bash hat sprite sheet (yep, back then the hats used a sprite sheet instead of being in svg format) included an unicorn face (1).
Albeit only a troll added to throw off users that would attempt to look for secret hats in the base hats spritesheet, this would start the trend of unicorn-based references in Winter Bash. What is really funny though is that this "precursor" of all Winter Bash weaponized ponies is not just any unicorn: she is actually Twilight Sparkle, from Hasbro's My Little Pony: Friendship is Magic.
But that's not all: Winter Bash 2012 also included an actual "unicorn themed" hat.
That hat would keep coming back every now and then, until 2020 when the rise of the Holy Order finally replaced it with its insignia.
From now one, the Defenders would rise every year to take up the new challenge and wear their hat with pride.
But... this doesn't really answer, right? After all, you were asking for an actual picture of Sparkles, not just an hat.
For this we will have to go back even more, up to the 2012 edition of Winter Bash. It was then that for the first time someone saw a blurry glittering figure dancing in the snow (2).
It was a dazzling sight indeed, so awestruck were the users that somepony even composed an haiku to forever remember that meeting.
yuki ni kirameku
no fuyu no chōkō
glittering in snows
sign of winter
The unicorn would then disappear from the site for many years, while a chicken took their place.
Later, in 2020 the unicorn was finally mentioned again and given an official name: she would hereafter be known as Sparkles (rif: 1, 2, 3, 4), and since then she has been a constant presence every Winter Bash.
Sadly, even after two separate rescue missions, no one remembered to bring a Kamera to take a picture of our friendly unicorn. Or perhaps the Shield of Boringness (4) is so powerful that no one actually remembers to take the picture in the first place. Like a certain wizard said, the only existing pictures of the latest sighting are those taken from far away as the rescue party was still trying to reach Sparkles as she got lost again last year.
Sadly this is all we know so far. It is up to you, my dear reader, to decide what do you want to believe: is Sparkles the purple shadow seen in the older picture or the white figure from last year? Only Yaakov may know...
(1) be honest, an unicorn based hat was also present in the 2011 edition of Hat Bash, an event held on the Arqade site that is the precursor to the network-wide Winter Bash we have today.
(2) if you were observant, you will have noticed that the "Twilight Sparkle" face appeared in the sprite sheet the year after I made the joke about the purple unicorn looking similar to her. Then later on Yaakov would call the unicorn Sparkles. Coincidences? Deliberate trolls? You decide :P
(3) in case you wondered the unicorn is indeed a "she". "oh where, oh where has my unicorn gone? oh where oh where can she be?" (4) "The Shield of Boringness lets unicorns go about their business without being disturbed. It means a unicorn could walk past a shop window and no one would bother to even look at it" - see Phoebe and Her Unicorn
(posting this separately for sake of completion)
While this is not directly tied to Sparkles, this may still be related somehow as the idea for Sparkle could be an homage to this one.
Once upon a time, Stack Exchange used to have an unicorn plush mascot.
Then someone started an odd tradition - the plush would be sent from one employee to another, as they took picture of hear "trip" and posted them online.
That was until the plush was finally lost in transit and never found again. That plush was called Lady Stackicorn, and she is still fondly remembered by many Stack Exchange members.
She never was Sparkles the unicorn from Winter Bash, but maybe our new friend is a way to keep alive the memory of a poor fluffy lady that went lost in the dark abyss of an unreliable mail service.