Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
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
Dark blue concrete wall with some small dust spots.
Source Atle Mo
Geometric lines are always hot, and this pattern is no exception.
Source Listvetra
Continuing the geometric trend, here is one more.
Source Mike Warner
The image depicts a seamless pattern of a Japanese family crest called "chidori" in Japanese .A chidori in Japanese means a plover in English.
Source Yamachem
Clean and crisp lines all over the place. Wrap it up with this one.
Source Dax Kieran
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
A light gray background pattern with seamless fabric-like texture and almost unnoticeable stripes.
Source V. Hartikainen
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
Nothing like a clean set of bed sheets, huh?
Source Badhon Ebrahim
This metal background pattern resembles a metal plate with rivets. Solid rivets on a metal plate.
Source V. Hartikainen