The question is better phrased as "What parts are actually made solely for/by Seat" apart from body panels, glass, trim and badges...
That's a tough one
I think the inside door cards, the tail lights, the rear parcel shelf and the wheels?
And possibly the speedo and tachometer. Apart from that you may as well be in an old style A3/Golf for all the difference it makes!
You won't find any main engine/transmission parts that are unique to the LCR, they all seem to have cropped up on another VAG car at some point or have the 'logo' stamped on them.
Even when I ordered my 'exclusive' LCR red checkered flag car mats from the Seat stealer, they arrived with a
sticker with Volkswagen parts printed on it. So they were made by the usual VAG suppliers it would seem as all the other mats.