Here is my initial “brainstorm list” I made up a month ago, before I had watched any movies for inspiration (although I had read some reviews of some to get an idea what to watch).
My general idea is that the Island has some kind of “zone” structure, maybe in concentric “rings” that get smaller the closer to the center of the Island you get.
These would be in the outermost zone, maybe getting to the border with the second zone.
“Jungle of the Savages” – here live several bands of primitive human hunter-gatherers that endlessly raid each other in a struggle for territory; some may be cannibals!
“Valley of the Gargantuas” – here two enormous semi-humanoid creatures eternally fight and wrestle with each other; they ignore puny visitors, but their struggles make the area very hazardous (ground shakes, boulders dislodged, etc.).
“Cliff of the Cave-Women” – here are several cave entrances that lead into the cliffside; this is the home of an all-female clan of primitive humans (female children are raised by the Cave-Women, while male children are brought to “The Tower of the Jeweled Ones” shortly after birth).
“Lair of the Reptile-Men” – cave entrances that lead to a network of caves and tunnels beneath the ground; the Reptile- Men (troglodytes?) are the traditional foes of the Cave-Women.
“River of Fire” – this is a shallow channel filled with molten lava that separates the outermost zone from the second zone of the island.
“Tower of the Jeweled Ones” – this is a perfectly symmetrical hexagon-shaped tower of some strange stone; the “Jeweled Ones” are mysterious beings that rarely leave their tower. The Cave-Women leave male offspring in the vicinity, which are then collected by the Jeweled Ones and brought into the tower. The Tower is near the edge of the River of Fire.