This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Seamless Light Background Texture.
Source V. Hartikainen
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
An attempt for cleaning up the original image in a few steps.
Source Lazur URH
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Turn your site into a dragon with this great scale pattern.
Source Alex Parker
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki
Inspired by a JPG that was uploaded to Pixabay by kokon_art
Source Firkin
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Abstract Geometric Background 2
Source GDJ
A seamless pattern based on a tile that can be achieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Remixed from a drawing in 'Analecta Eboracensia', Thomas Widdrington, 1897.
Source Firkin
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen