Adventures in concepts and stuff

So out of the 20 ideas that was listed a post or two ago i've decided on #8.

The concept I want to work with is the idea of players being forced to work together when they know its not guaranteed to end in their favor. To achieve this, I plan to have four players working towards a goal that, while only one can achieve, all four must participate for it to happen. I want players to have to deal with the conflict of having to work with players while knowing that in the end everyone is working for themselves. The biggest challenge will be choose the right time to turn on the other players; If a player acts too fast, he'll risk the other 3 players turning against him, and if they act too slow then he'll end up losing.

Theme statement: "Teammates are only temporary"

As for the setting, It has to be a environment where:
A. adventurers can be trapped in,
B. adventurers have to be rescued from via some form of transportation (like it couldn't be a forest, because then question of "why doesn't the player just run out of the space?")
C. a place adventurers could logically get stuck in (like a cave or...yeah a cave)

So heres the pitch: A team of 4 archeologists descended into a cave researching the existence of an ancient Mayan (or any other ancient civ) mythical beast. However, on the way down their lift malfunctions and they end up falling down a part of the way, scattering themselves and various equipment around the cave floor. Normally, this wouldn't be too much of an issue, as they could just radio back up to the surface for an extraction, but their radio was broken into 4 pieces and scattered with the rest of their stuff. To make matters worse, the Mayan beast wasn't so mythical at all, and is now trying to kill them. So the archeologists must find the pieces to the radio and assemble it, all while avoiding the beast trying to kill them. To make matters worse, the rescue can only save one of them before flying off, leaving the other two behind for multiple hours, dooming them to the monster. (as the helicopter thats coming to save them only have enough room for two and would have to drop them off and refuel)

As for the art style. I'd like to avoid any high detail work (as its simply not in my skillset) but would also like to give it a dungeon crawler feel to it (think World of Warcraft)

Some examples:

 Heres an already existing board game, Cave Troll, that somewhat captures the look i'd like to go for.

As for a color palette - I feel like my options are somewhat limited to a earthen dungeon. However, this tetrad captures the look i want to go for (maybe i'll add some more yellow, but i doubt it)