You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
Seamless SVG vector and JPG backgrounds with faded diagonal stripes. The colors are editable.
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
This background pattern looks like bamboo to me. Feel free to download it for your website (for your blog perhaps?).
Source V. Hartikainen
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
Light gray version of the Binding pattern that looks a bit like fabric.
Source Newbury
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
The tile can be had by using shift+alt+i on the selected rectangle in Inkscape
Source Firkin