Okay so,
Imma just kinda do shit here

So you know the Sanders sides posters (I'll have pics in a sec)
There's a lot of little details that people seem to miss

I'll start with the ones I've seen pointed out, and they're on Patton's poster

In the pic, there's crayons near Patton. That might not seem significant, but stay with me
To the left of him, there's a red, a purple, a yellow, and a broken blue crayon, and to the left, there's a pink, an orange, and a green crayon, and a lot of people think they represent the other sides
Red - Roman|Yellow - Deceit|Blue - Both Patton and Logan|Purple - Virgil
And with the colors we don't associate with sides(Orange, Green, and Pink), they could represent the "dark sides" that we don't know about yet.

I don't think there's a lot to talk about with Virgil's, other than the fact that I love it, but one thing that I don't think a lot of people really point out is the three ghost-like things in this one. I dunno, I wanted to point it out.

Logan's is cute. I like Logan's. He has his Ravenclaw scarf at the top of his desk thing, I like that, but what I love about this one is, right above the microscope, there's a picture of Virgil, Patton, and Roman, and it's fricking adorable. The box labeled 'Vocabulary cards' and the giant chess piece on top of it are great, too. I love my nerdy boi.

Roman's is honestly pretty cool. And at first glance, I didn't see it, but the fucking dragon witch is in the background and I love it.

NEXT UP:
The color wheel theory

This theory suggests that Virgil isn't/wasn't a dark side, and that Deceit is his parallel, among other things.

Here's a color wheel
Now, I'm not really sure if I'll do a great job of explaining it,
but I'll try

So, the sides seem to be partially represented by color, Roman-red, Virgil-purple, Logan-indigo, and Patton-Blue
And would you look at that
They're all on the same one side of the color wheel
Remember that

Okay, so Virgil has said he aims to protect Thomas. As his anxiety, he keeps Thomas vigilant, and basically takes care of him.
That doesn't sound like something a "dark side" would do
Let's compare that to Deceit.
Deceit is, well, deceitful. He lies to Thomas, and he does so to give him a false sense of security, the opposite of what Virgil wants to do for him.

Now, what color do we associate with Virgil, again. Oh, right, purple.
And what's opposite of purple on the color wheel?
You guessed it
Yellow
And what color does Deceit wear?
Puke fuckin' yella
(I'm literally just going off of memory, I'm sorry, but I swear there's more evidence than that)
"But wait," I hear you saying. "How does that prove Virgil wasn't a dark side?"
Well, my dear Watson, simply look at the colors next to purple
Red, Indigo, and blue.
The same colors associated with Roman, Logan, and Patton.
(Along with the mysterious pink)

And with this theory, we can assume that whoever Roman's, Logan's, and Patton's dark parallels are, they're opposite on the color wheel as well- So Roman's would be associated with green in some way, and Logan's and Patton's would be orange

That's all I got for now