Before starting, read the Data Analysis page on how the game works.
Modding files Edit
The game cd ISO file be modded using the program CDmage. Replacing existing files in the ISO file with equivalent size is known to work. This has worked when the file sizes (before and after modding) are equal.
Modding textures Edit
Can be done using the program TIMviewer. This has worked when using the same height, width, color depth and color palette.
Use TIMviewer to export the texture to BMP. Open the new BMP file in MS Paint. Copy the picture you want to replace it with and paste it into Paint. Make sure that the height and width are unchanged. To re-convert the file from BMP, use TIMviewer to open the BMP file. Decrease the color depth so that it returns to its old depth. Export the file to a new TIM file. Now make sure that the file name and file size of the new file is identical to the old one.