This patch allows you to load custom (Ex)GFX files for each of the 7 castle destruction cutscenes. To do so, just edit the tables sp1-sp4,fg1-fg3,bg1 in the asm file.
Note: you can't insert GFX files in slots BG2-BG3, and you can only use (Ex)GFX numbers $00-$FF.
A fine patch for anyone looking to spice up the castle cutscenes, though it's held back some by the inability to change the tilemaps around (can change the tile graphics but not how they're arranged). Still, a creative mind can play around this limitation to make something fresh.