I'm working on a tree skull art design for a Fiverr client and the idea was based on a facebook image that had a tree with a few hidden faces in it. You can check out the Fiverr gig right here - I'll draw a horror skull in black ink for $5
The challenge with this piece of art was to make the skulls look almost hidden within the tree itself. In the pencil drawing above I think I'm getting away with it. I need to ink this.