Whether you are patching a ROM to create a "Kaizo" difficulty hack or just drawing fan art of Saffron City, mastering these tiles is the first step to becoming a true Pokemon cartographer.
This proves that the base tile set is not static. You can overwrite the "Unused" tile slots (slots 0x200 to 0x2FF) with your own custom graphics. Many ROM hackers replace the Sevii tiles with original designs for fan games. pokemon fire red tile set