I really like the aluminum metal door sills but unfortunately even after a year of use, they are already quite a bit scratched up. So I decided I'd go for the carbon fibre look.
I found some good looking sticker on http://www.rpmtesla.com. Honestly I was a little worried about how the final product would look once applied, but I think the stickers did turn out quite nicely.
They were easy to apply even though I had to remove them many times until they fit perfectly. This 3M material is very sturdy and you can easily remove it again and again as long as you don't press it on too hard.
They also are cut to perfectly fit on to of the aluminum door sills. I had to swap the stickers from side to side to get a really perfect fit tough.
So here's the final result: