I see you divided it into four parts internally.
The reason is much simpler than you might think. The game limits the maximum image size to 4096, but to ensure the image stays clear when enlarged, I created a new image at 8192. Then, by reducing it to 50%, it matches the original size but with a higher resolution.
Anyway, hope I wasn't too annoying speaking about things I don't really know that well.
Feel free to provide more feedback, and don't worry about it!