CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
From a drawing in 'From Snowdon to the Sea. Striking stories of North and South Wales', Marie Trevelyan, 1895.
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A heavy hitter at 400x400px, but lovely still.
Source Breezi
Thin lines, noise and texture creates this crisp dark denim pattern.
Source Marco Slooten
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 version without colours blended together to give a different look.
Source Firkin
High detail stone wall with minor cracks and specks.
Source Projecteightyfive
Alternative colour scheme. 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
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
Redrawn based on a drawing in 'По Сѣверо-Западу Россіи' Konstantin Sluchevsky, 1897.
Source Firkin
This is sort of fresh, but still feels a bit old school.
Source Martuchox
A seamless background tile of aged paper with shabby look.
Source V. Hartikainen
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
Zero CC asphalt, pavement, texture, photographed and made by me. CC0 WARNING I FOUND A SEAM ON THIS TEXTURE
Source Sojan Janso
White handmade paper pattern with small bumps.
Source Marquis
Seamless SVG vector and JPG backgrounds with faded diagonal stripes. The colors are editable.
Source V. Hartikainen