Let's see, the courtroom uses tileset 1C. According to the location tileset data, that tileset uses tile packets 96, 97, 98, 99, 9A, AF, and 13.
Those packets should be at 2C0000, 2C0E5D, 2C1B72, 2C2786, 2C36D6, 2FD02D, and 257CBF.
Be careful, whichever tileset you actually modify, the graphics might take more space than the original and will have to be repointed.