From a drawing in 'Danmarks Riges Historie af J. Steenstrup, Kr. Erslev, A. Heise, V. Mollerup, J. A. Fridericia, E. Holm, A. D. Jørgensen', 1897.
Source Firkin
Colour version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
From a drawing in 'From Snowdon to the Sea. Striking stories of North and South Wales', Marie Trevelyan, 1895.
Source Firkin
An orange vertically striped background pattern. Feel free to download and use this orange background pattern, for example, on the web). It resembles a wallpaper with vertical stripes or something similar to it.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
A seamless web texture with illustration of pale color stains on canvas.
Source V. Hartikainen
Tile-able Dark Brown Wood Background. Feel free to use it as a background image in your designs or somewhere on the web. By the way, the color seems to be close to Coffee Brown.
Source V. Hartikainen
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Continuing the geometric trend, here is one more.
Source Mike Warner
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
A version without colours blended together to give a different look.
Source Firkin
A nice and simple white rotated tile pattern.
Source Another One
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Alternative colour scheme to the original.
Source Firkin
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba