CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
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
Light gray version of the Binding pattern that looks a bit like fabric.
Source Newbury
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Colorful Floral Background 3 No Black
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
The original has been presented as black on transparent and stored in the pattern definitions. To retrieve the unit tile select the rectangle in Inkscape and use shift+alt+i
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
Sort of reminds me of those old house wallpapers.
Source Tish
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
If you don’t like cream and pixels, you’re in the wrong place.
Source Mizanur Rahman
You know, tiny and sharp. I’m sure you’ll find a use for it.
Source Atle Mo
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Prismatic Abstract Geometric Background 2
Source GDJ