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
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A very slick dark rubber grip pattern, sort of like the grip on a camera.
Source Sinisha
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
A repeatable image with dark background and metal grid pattern.
Source V. Hartikainen
Prismatic Snowflakes Pattern No Background
Source GDJ
Black And White Floral Pattern Background from PDP.
Source GDJ
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
One more sharp little tile for you. Subtle circles this time.
Source Blunia
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
Subtle scratches on a light gray background.
Source Andrey Ovcharov
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Here's a new gray "fabric" pattern. Use it as backgrounds for websites or for other purposes.
Source V. Hartikainen
If you’re sick of the fancy 3D, grunge and noisy patterns, take a look at this flat 2D brick wall.
Source Listvetra
More carbon fiber for your collections. This time in white or semi-dark gray.
Source Badhon Ebrahim