Monsters, myths and legends definitely.
The unknown is interesting......
Imagine creating something based off of a lone (yet real) eye witness account?
By "real" I mean real to that person. But a mystery and unproven to everyone else.
Like an Alien from a specific incident..the devil, an angel, a monster, whatever it is.....an interpretation of a story told - a story that the storyteller swears to be true.
I love that thought of "what if?", "what if his story is true?", "what if he was abducted by aliens and they looked like this?".
Sideshow's backstory to their interpretation of the Grim Reaper is amazing. Sadly it's all made up.
But it would have been cool if they could have said this version of the Grim Reaper is based on this person's sighting and description.
An element of "what if?" would make any piece interesting to me. I'd have a story to tell around the piece - there would be a conversation to be had. And the piece would have an air of mystery....