Classic 5v5 competitive defuse map based on Islands such as Migingo and Santa Cruz Del Islote.
You're likely to see a mix of water, man made structures, dirt paths, caves, trees and technology. I would imagine a contrast between very high tech equipment and very low tech / natural foliage in the environment.
The mood board idea is contagious, so here are some general ideas to start this project with
Here are some videos I found on Youtube.
Difficult Life At Migingo Island, this is a heavy documentary although there are parts of bigger fictional stories that can be extracted from the video.
Living on the Most Crowded Island on Earth