Since everyone is agreeing to the island, here is the information I have for you folks about it so far. 

Y/N's private island is based on DK Island and Wumpa Island from Donkey Kong Country Returns/Tropical Freeze and Crash of the Titans/Mind Over Mutant (as you are aware of). 

It is located across the sea and it's impossible for anyone to find it, except for Y/N's faction, his friends/allies, and his harem. And if someone did find it, well, let's just say they have a death wish from the island's dangerous creatures and deadly traps. 

This large island has a lot of worlds/landscapes to explore, each considered their own habitats, culture, and civilizations. It's also connected to some smaller islands as well. 

1. Jungle: The Jungle is a jungle with dense vegetation and tall trees, and presence of some ruins (similar to ones in the Ruins). 

2. Lost Mangroves: Lost Mangroves is an island located near Y/N's island. It got its name due to the presence of abundant mangrove trees accompanying its sandy beaches. Aside from natural wonders, the island is covered in wreckage from planes and mine cart rails were built around several of the island's trees.

3. Beach: As the name suggests, it is a tropical beach-themed world. Considering the proximity to the sea, the levels in this world can be considered water areas.  

4. The Ratcicle Kingdom: (also known as Frozen Coast) Located on the eastern coast of the Jungle, the Ratcicle Kingdom is made almost entirely of ice. The two are connected by a series of land bridges. A bastion of civilization in what is otherwise a frozen wasteland, the Ratcicle Village is built into the peak of a mountain and boasts tall, gothic architecture. It is inhabited by scrawny Ratcicles who are friendly to Crash and may offer him directions. 

Most of the townsfolk can be found in the lower half of the village, standing near an ice sculpture of a Ratcicle. The upper half is mostly barren, but contains two paths leading out from the village. The northeastern leads to the Ice Prison while the northwest leads to Evil Public School. 

5. Ice Prison: The Ice Prison itself is a cavernous area with many natural and unnatural obstacles designed to keep prisoners from getting out or getting in. The cavern eventually diverges into two paths. The first path, to the north, leads to the core of the Ice Prison while the second path  chunks of ice flow down a waterfall. 

6. Autumn Heights: Autumn Heights is a large grassy mountain island in the water which has habitats of red and yellow trees, windmills, pine trees, monoliths, and mountains with one in the shape of an owl. 

7. Ruins: The Ruins is a group of ruins and monuments, build by an ancient civilizations. These ruins have also a still-running waterway and an artificial waterfall which falls into the sea.

8. Wasteland: Dry and inhospitable, few things live here save for crows, flowers, cacti, and hostile creatures. The Wasteland is west of the Ruins, connected to it through a decrepit coliseum. Beyond the coliseum is a section of canyon, where cracked stone walls, falling boulders, quicksand, and more. 

A tunnel leads out to a sandy clearing. One of the Wasteland's most notable landmarks, this huge expanse of desert acts as an arena of sorts for RhinoRoller to bound about in. 

9. Bright Savannah: The savannah appears as its own island decorated tall grass, Baobabs and Umbrella Thorn Acacias, boulders, canyons, and a waterfall. The Savannah also as its own puppets of animals, has a hidden tornado and is being attacked by fire in the southeast. The canyons of the island are shown with gears and cogs part of their own contraptions on the west and infested with vines having thorns on the east. 

10. Cave: As the name suggests, this world takes place in a dark, treacherous cave. It is plagued by Mole Guards, who cause tremendous damage to the caves by throwing bombs or pickaxing down rocky spikes.

11. Crystal Mountains: The world is on a high mountain with multicolored crystals everywhere. 

12. Evil Public School: It is located in the mountains north of the Ratcicle Kingdom, with deadly school traps such as electric fences, spiked, mechanical rollers, and volcano-cannons that fire flaming chicken breasts. 

13. Sea Breeze Cove: Sea Breeze Cove is an atoll with many palm trees living on them as well as a diverse ecosystem of sealife living around. This atoll is where a small keep was built by an unknown group.

14. Forest: As presumed by the name, this world is a forest with large trees and dense vegetation. There are many artificially made structures, like wooden walkways and suspended platforms high above the ground, sometimes, going through trees. Treehouses, totem poles, wooden carvings and hanging cut logs are also present.

15. Lumber Yard: It is a deserted wasteland located high on the island near the Factory. It consists of saw-like machines that cut down tress and sawing away at vegetation. 

16. Juicy Jungle: Juicy Jungle is an island with lush jungles covering most of it. Its trees seem to produce large amounts of fruits, motivating the construction of a juice and popsicle factory on the island. The island's lower ground is frozen and most likely where the popsicles are made. 

17. N. Sanity Island: An island that has a statue at the centre of it. Inside the statue is a weapon factory for building weapons. 

18. Cliff: The Cliff is an ancient giant mountain, with a desert-like terrain, that has some artificially made wooden platforms for access. The area has fossils of extinct sea creatures and dinosaur skeletons. There is also the presence of some ferocius and undead skeleton creatures. The rocky terrain is very frail due to its prehistoric age, and in some parts, can barely support almost anyone's weight. 

19. Uka Tree: The largest tree located above the Forest. Inside that tree has several caves filled with toxins. It even has lab made for creating Mutants at the outer branches and slopes at the very top of the Uka Tree. 

20. Factory: This world takes place on an industrialized area. Most of the levels are located inside the factory, featuring heavy machinery and robots. People have to avoid hazards created by mechanical devices. 

21. Junkyard: A bleak and polluted place, it is littered with heaps of garbage and the rusted scraps of felled doomsday devices. 

22. Mount Grimly: It is located situated on an island north of the Junkyard. Mount Grimly lies in the middle of the sea, and is connected to the Junkyard only by a series of narrow land bridges. The inside of the mountain is dark and cavernous, with stalagmites abound and steep drops into a murky abyss with a number of five chambers.

23. Volcano: The Volcano is a very dangerous world, and as its name implies, it takes place in a volcanic area. This volcano has main and side vents, lava tubes, a magma chamber, a magma reservoir, and a caldera. There are structures that sink into the lava when stepped on and platforms that appear for a set period, then sink back into the lava, fireballs that move in a set pattern.

I hope you guys like what I've done with the island so far. I will be revealing the creatures of the island soon. 

If you have any ideas for the island you would like to add, let me know at the comments below. Peace out and enjoy!