Quite hard, because all the backgrounds are bitmaps. It's an unfortunate era for that - Final Fantasy X looks fantastic on a modern system, because it can be rerendered at higher resolution.
In my retroactively ideal world, Square would have had had the foresight to render FFVII at 1080p and downscale at runtime for the playstation - then even today, 15 years later, we could load the game up in an emulator and unlock enough detail to max out a modern HD display.