The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
Prismatic Groovy Concentric Background
Source GDJ
You know I love paper patterns. Here is one from Stephen. Say thank you!
Source Stephen Gilbert
Tiny little flowers growing on your screen. Nice, huh?
Source Themes Tube
These dots are already worn for you, so you don’t have to.
Source Matt McDaniel
Prismatic Snowflakes Pattern No Background
Source GDJ
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Remixed from a drawing in 'Очерки Русской Исторіи въ памятникахъ быта', Petr Polevoi, 1879.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
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
CC0 and seamless wellington boot pattern.
Source SliverKnight
Abstract Tiled Background Extended 11
Source GDJ
Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
More carbon fiber for your collections. This time in white or semi-dark gray.
Source Badhon Ebrahim
Lovely pattern with splattered vintage speckles.
Source David Pomfret
A dark pattern made out of 3×3 circles and a 1px shadow. This works well as a carbon texture or background.
Source Atle Mo
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Retro Circles Background 8 No Black
Source GDJ
The original enhanced with some gradients.
Source Firkin