Sorry this has taken me so long to put together, real life intervened :P
If you haven't already read
What I Already Knew, you might want to go do that first because some of these images and their descriptions will be vaguely spoiler-y. Just so you know.
None of these images are mine.
I owe Britt another thank you for finding all of these, and brainstorming them for me - even if she was just trying to procrastinate essays at the time :P
First up, people! There are really only two OCs in this, and they're characters that are routinely put into fanfic anyway. I didn't really stray from common fandom-imaginings of them in terms of appearance.
The lovely Victoria Anderson is forever played by Lea Salonga. I randomly stumbled on these pictures as I was making this post and they're perfect.
The second OC is Elliana Hummel, Kurt's mother. Again, she's forever and always Amy Adams in my head. It just so happened that she looks amazing wearing the Royal Blue of the Hummel reign. The second photo is particularly apt in how I pictured Ellie as Queen.
And now, for headpieces! Britt and I dubbed the separate kingdoms with colours, and so I'll put those headings in here to split them all up.
Sapphire Kingdom - otherwise known as the Hummel-Hudsons
Burt's crown
Carole's crown
Finn's circlet (shh pretend it's silver)
Kurt's official circlet (except there is only one central stone)
Ellie's informal/engagement tiara that Kurt prefers wearing (mentioned in the first part)
Ellie's formal crown
Amethyst Kingdom - aka the Berrys'
Hiram and Leroy, informal crowns (they both have slightly different versions)
Hiram and Leroy, formal crowns (again, similar but not exactly the same)
Rachel's tiara (my personal favourite, if I had to choose)
Intended headpieces for the arranged marriage (the ones presented at their respective 16th birthday celebrations)
Kurt
I can't embed it here, so
here's the link - it's gorgeous and is an actual circlet that someone made :)
Rachel
And the official headpieces worn when the two separate couples married. Yes, Rachel did get her Princess status back. Sort of.
Kurt and Blaine
Rachel (admittedly less elaborate than this, but along these lines - also, it would be blue now that I think about it)
Finn (again, it would be blue)
That night was a lot of fun. The story did change somewhat between our discussions then and the final product, hence the colour changes and things. If I think of any other visual extras I'll be sure to add them!