Here's an idea of a simple marking that covers lion's head and softly fades at the neck.
Onyx Head:

And some recolors:

Ans also here's an exapme of a Brown Head in action with White base, Henna Cheetah and Under white:




If you liked this, check out my other ideas:
Zombie base
Berry bases
Badgerface, Brindle, Blaze, Star and Freckles markings
Base&Manebase ideas
Silky mane
Mutation: OG Mane