This beige background pattern resembles a concrete wall with engravings or something similar to it.
Source V. Hartikainen
Gold Triangular Seamless Pattern No Background
Source GDJ
It’s an egg, in the form of a pattern. This really is 2012.
Source Paul Phönixweiß
You know you can’t get enough of these linen-fabric-y patterns.
Source James Basoo
A free pink background pattern.
Source V. Hartikainen
A new take on the black linen pattern. Softer this time.
Source Atle Mo
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
A pattern derived from part of a fractal rendering in Paint.net.
Source Firkin
Green Web Background, Seamless tile.
Source V. Hartikainen
Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.
Source Firkin
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
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
Submitted in a cream color, but you know how I like it.
Source Devin Holmes
Formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing of the coat of arms of the Ottoman Empire on Wikimedia.
Source Firkin
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
A seamless tessellation pattern. To get the tile this is formed from, select the pattern in Inkscape and use shift+alt+i.
Source Firkin
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
The basic shapes never get old. Simple triangle pattern.
Source Atle Mo
Classy golf-pants pattern, or crossed stripes if you will.
Source Will Monson
CC0 and seamless wellington boot pattern.
Source SliverKnight
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A nice and simple gray stucco material. Great on its own, or as a base for a new pattern.
Source Bartosz Kaszubowski
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin
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
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin