I don't think there any actual cels for SIGN because by then they'd gone digital coloring right? 'Tis a shame, I'd love some. And Madlax... and El Cazador.
I've nabbed some Noir and Arc the Lad cels, though. Never managed to get a really good Chloe one, I needs it to round out my set. There's a really awesome one of Chloe and Kirika that's been on sale for a couple years on ebay, but it's something like $500 so a little more than I could ever justify on a hobby unless I win the lotto.
Several .hack//SIGN sketches.
If my scanner wasn't 15 years old and unable to do them proper justice I'd upload some pictures.