A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Derived from an image that was uploaded to Pixabay by Kaz
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
A blue gray fabric-like texture for websites. An yet another fabric-like texture. It has subtle vertical and diagonal stripes to it.
Source V. Hartikainen
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
From an image on opengameart.org shared by rubberduck.
Source Firkin
This is the third pattern called Dark Denim, but hey, we all love them!
Source Brandon Jacoby
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Psychedelic Geometric Background No Black
Source GDJ
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
There are many carbon patterns, but this one is tiny.
Source Designova
This one is amazing, truly original. Go use it!
Source Viahorizon
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A light brushed aluminum pattern for your pleasure.
Source Tim Ward
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen