@Griffin-McPherson I use character sheets just as a fun exercise, but do not include them in my picture book portfolio, because for picture books, you want to show how you create picture books, not character sheets, I think? But maybe I am wrong. 🙂
And I did use for my portfolio some illustrations I've originally done as a character sheet, but I put them there separately.
When I think about it, I even didn't send a character sheets to my editor when working on a picture book. I did sent "development" sheet, when we were brainstorming about how the character should look like and what style would be the best for this specific book. (I would not place that on my portfolio)
styl.jpg
After that, I've done just one illustration with the approved character and used that as a reference for me when working on the book... (also not for my portfolio though)
betka_rozkres.jpg
And as @NessIllustration said, I would rather focus on having some nice sequential art on your portfolio!
SnÃmek obrazovky 2023-01-08 v 12.35.17.png
It doesn't have to be a ton, but it should show that you can stay consistent with your characters (this you could do on the character sheet) and how you are able to place them on a page, background and everything (character sheet is useless for this).
But - social media looove characters sheets! So if you like to create them, do it! And post it 😉