This one is amazing, truly original. Go use it!
Source Viahorizon
There are many carbon patterns, but this one is tiny.
Source Designova
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
A classic dark tile for a bit of vintage darkness.
Source Listvetra
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
A seamless pattern the starting point for which was a 'light rays' rendering in Paint.net.
Source Firkin
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
Prismatic Basic Pattern 2 No Background
Source GDJ
A yellow tiled background... Blurriness, bokeh effect and rectangles pattern in one mix.
Source V. Hartikainen
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
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
Prismatic Abstract Geometric Background 5
Source GDJ
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Number five from the same submitter, makes my job easy.
Source Dima Shiper