Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
An abstract web texture of a polished blue stone (or does it look more like ice).
Source V. Hartikainen
The starting point for this was drawn on the web site steamcoded.org/PolyskelionMaker.svg
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
A re-make of the Gradient Squares pattern.
Source Dimitar Karaytchev
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A seamless pattern formed from miutopia mug remixes on a tablecloth.
Source Firkin
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
Have you wondered about how it feels to be buried alive? Here is the pattern for it.
Source Hendrik Lammers
Tiny little flowers growing on your screen. Nice, huh?
Source Themes Tube
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Pattern produced in Paint.net using the Vibrato plug-in.
Source Firkin
A nice and simple white rotated tile pattern.
Source Another One
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
Zero CC tileable hard cover cells, skin like, book texture. 4K, Scanned and made by me CC0
Source Sojan Janso
A repeatable image with dark background and metal grid pattern.
Source V. Hartikainen
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin