If you want to do the biggest and most ambitious game ever, choose China.
If you want to focus on mythology, choose India or Mexico.
If you want to design varied Pokemon creatures, choose Brazil, or Colombia.
The Nayam region will have some regional variants of Pokemon originally from other regions!
Let's start with some who originated in Unova!
Nayamean Joltik and Galvantula will be Bug/Dark, and based on the Mexican red-kneed tarantula.
Nayamean Purrloin and Liepard will be Fairy type, and have a final evolution called Alebruma (a Fairy/Flying type whose name derives from Alebrije [a type of brightly colored statue common in Mexican folk art] + Puma [AKA Mountain Lion/Cougar]
Nayamian Axew, Fraxure, and Haxorus are Dragon/Rock-type Pokemon that are influenced by traditional Aztec weaponry made out of Obsidian
And now, for some information on the fossils found in Nayam!
If you have the Hoof Fossil, you can resurrect the Ogre Pig Pokemon Entellet. It is a Rock/Dark type that lived in the forests of Nayam. It evolves into Chernohog. Based on the "terminator pig" Daeodon.
If you have the Tail Fossil, you can resurrect the Great Lizard Pokemon Varanoob. It is a Rock/Poison type that lived in Nayamean deserts. It evolves into Noxania. Based on the large extinct lizard known as Megalania.