Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
You know you can’t get enough of these linen-fabric-y patterns.
Source James Basoo
Utilising a bird from s-light and some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
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
Vertical lines with a bumpy, yet crisp, feel to it.
Source Raasa
Number 5 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
From drawing in 'Musings in Maoriland', Thomas Bracken, 1890.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion
Heavily remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
More leather, and this time it’s bigger! You know, in case you need that.
Source Elemis
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Based on an image that was uploaded to Pixabay by devanath
Source Firkin
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
Super detailed 16×16 tile that forms a beautiful pattern of straws.
Source Pavel
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin