Reznor: That's probably what SquareSoft did, simply re-render the scenes in the higher resolution. Actually, It was probably easier for them to do that, since they probably still had the psx files in a decompressed form, still ready to be edited, when they decided to make a pc version.
Ficedula: Sorry for causing the choking! Still, technically, you do have the source code. I believe its in a little file called "FF8.exe". Actually, since the midi config runs the game using a different executable ("PlayFF8.exe") that was based on the original executable, it sounded to me like editing the source code was feasible. But hey, like I said earlier, I'm no graphic programmer.