Celes Amano Sprite sheet

That's awesome. How about IPS patches and ASM hacks. Will expansion eff those up at all?

Expansion only make your ROM size bigger. It does not affect code. Certain patches and ASM hacks affect offsets beyond regular ROM size so it's better to have made the expansion before using them, otherwise it could result in a non-regular ROM size and certain emulators and real hardware would not play the ROM.