One more updated pattern. Not really carbon fiber, but it’s the most popular pattern, so I’ll give you an extra choice.
Source Atle Mo
A heavy hitter at 400x400px, but lovely still.
Source Breezi
A seamless pattern recreated from an image on Pixabay. It is reminiscent of parquet flooring and is formed from a square tile, which can be recovered in Inkscape by selecting the ungrouped rectangle and using shift-alt-I together.
Source Firkin
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Black brick wall pattern. Brick your site up!
Source Alex Parker
Might not be super subtle, but quite original in its form.
Source Alex Smith
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A free green background pattern with a pattern of rhombuses on a seamless texture. Feel free to use it as a tiled background image on your web site.
Source V. Hartikainen
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
The basic shapes never get old. Simple triangle pattern.
Source Atle Mo
Remixed from a drawing in 'Analecta Eboracensia', Thomas Widdrington, 1897.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin