For my idea on this project I have decided to have it be set out at sea. I have thought about making a medieval ship travelling out on a stormy sea, however I am also depicting a large aquatic dragon attacking the ship.
Here's a sketch to show a more visual interpretation of what I'm trying to go for:
In the water you could have some fragments from wrecked ships, as well as having a couple other ships, to make the scene look like more of alive instead of an attack on a single ship
I think you should add a cloud above it, so you can have that crack of lightning in the background. It would make a great addition to the atmosphere of the scene.
You could also do a kraken , in my opinion is much better idea.
I’ve just sent you instructions on how to claim your free Medieval Fantasy Cardboard viewer. Check your private messages here on the forum. Good luck!! 
