If you have a location you would like to feel unique or exotic, one thing you can do is use an entirely different monster book to populate the monsters and animals. This is especially important if you have experienced players who are familiar with the Monster Manual (and even other WOTC monster books such as Volo’s Guide or Tome of Foes).
This works great for isolated islands, portals to other worlds / continents, etc.
Some example monster books you can use:
- Tome of Beasts by Kobold Press
- Monstrous Menagerie from Level Up Advanced 5e
- Monster Manual Expanded
Let me know if you have any other favorite 3rd party monster books!