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
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
U.S.-based National Fire Protection Association standard fire diamond for flagging risks posed by hazardous materials. The red diamond has a number 0-4 depending on flammability. The blue diamond has a number 0-4 depending on health hazard. The yellow has a number 0-4 depending on reactivity. the white square has a special notice, e.g OX for oxidizer.
Source Firkin
This background pattern looks like bamboo to me. Feel free to download it for your website (for your blog perhaps?).
Source V. Hartikainen
A new take on the black linen pattern. Softer this time.
Source Atle Mo
I have no idea how to describe this one, but it’s light and delicate.
Source JBasoo
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
From drawing in 'Musings in Maoriland', Thomas Bracken, 1890.
Source Firkin
A brown seamless wood texture in a form of stripe pattern. The result has turned out pretty well, in my opinion.
Source V. Hartikainen
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
This is the remix of "Background pattern 115" uploaded by "Firkin".Thanks.
Source Yamachem
Prismatic Abstract Geometric Background 2
Source GDJ
Could be paper, could be a Polaroid frame – up to you!
Source Chaos
This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
Square design drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo