Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Remix from a drawing in 'Ostatnie chwile powstania styczniowego', Zygmunt Sulima, 1887.
Source Firkin
Pattern produced in Paint.net using the Vibrato plug-in.
Source Firkin
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
Dark Tile-able Grunge Texture. I think this texture can be classified as grunge. It's free and seamless, as always.
Source V. Hartikainen
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
Light gray paper pattern with small traces of fiber and some dust.
Source Atle Mo
Small dots with minor circles spread across to form a nice mosaic.
Source John Burks
From drawing in 'Musings in Maoriland', Thomas Bracken, 1890.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A light gray fabric pattern with faded vertical stripes.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A free seamless texture of reptile skin colored in a dark brown color. As always, you may use it as a repeated background image in your web design works, or for any other purposes.
Source V. Hartikainen
The image depicts a seamless pattern of a snow crystal.I referred to a book called ”sekka-zusetsu” or "雪華図説" which means an illustrated explanation about snow crystals.This book was published in 1832 (天保3年) or Edo period.For more about "雪華図説",see here:dl.ndl.go.jp/info:ndljp/pid/2536975
Source Yamachem
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
Embossed lines and squares with subtle highlights.
Source Alex Parker
If you need a green background for your blog/website, try this one. Remember that Green Striped Background is seamlessly tileable.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
An abstract Background pattern of purple twisty patterns.
Source TikiGiki
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
A free seamless background with pink spots.
Source V. Hartikainen
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin