CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
From a drawing in 'A Rolling Stone. A tale of wrongs and revenge', John Hartley, 1878.
Source Firkin
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
This one is amazing, truly original. Go use it!
Source Viahorizon
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
The classic notebook paper with horizontal stripes.
Source Are Sundnes
Zero CC tillable hard cover red book with X shape marks. Scanned and made by me.
Source Sojan Janso
From a drawing in 'Royal Ramsgate', James Simson, 1897.
Source Firkin
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i
Source Firkin
A heavy hitter at 400x400px, but lovely still.
Source Breezi
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
A beautiful dark padded pattern, like an old classic sofa.
Source Chris Baldie
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A seamless pattern formed from a rectangular tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
The image depicts a seamless pattern of Japanese Edo pattern called "kikkou-matsu" or "亀甲松" meaning " tortoiseshell-pinetree".The real pinetree is like this: https://jp.pinterest.com/pin/500744052301065077/
Source Yamachem
Little x’es, noise and all the stuff you like. Dark like a Monday, with a hint of blue.
Source Tom McArdle
I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
Love the style on this one, very fresh. Diagonal diamond pattern. Get it?
Source INS