How do you make new characters?

How to get out of comfort zone? Any good character creation tools?

I've recently finished some character designs for a comic I plan to do. I still need to do my second batch of the cast

But now I want to focus on practice on character concepts.

I have an idea for a world where it an apocalypse set within the backrooms lore and maybe a mix of the scp foundation as well

Basically one last city stands as the entire world has turned to ash, and some of it population is trapped in the backrooms while demons roam the planet.

I'm always stuck making new characters

And any advice for picking out poses for characters as well?