CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
The image a seamless pattern of a wire-mesh fence.I want you to use this pattern as a lower layer.
Source Yamachem
Continuing the geometric trend, here is one more.
Source Mike Warner
First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.
Source Atle Mo
A heavy hitter at 400x400px, but lovely still.
Source Breezi
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
Looks like an old wall. I guess that’s it then?
Source Viahorizon
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
Wild Oliva or Oliva Wilde? Darker than the others, sort of a medium dark pattern.
Source Badhon Ebrahim
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
Very simple, very blu(e). Subtle and nice.
Source Seb Jachec
Tiny little flowers growing on your screen. Nice, huh?
Source Themes Tube
Prismatic Snowflakes Pattern 2 No Background
Source GDJ
From a drawing in 'Jardyne's Wife', Charles Wills, 1891.
Source Firkin
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
Here's a seamless brown cork board background texture. Feel free to download or reshare if you like.
Source V. Hartikainen
The following free background pattern has glossy diagonal stripes as a texture to it, and it's colored in a light blue gray color. This background pattern is suitable for using in web design or any other graphic design projects. This applies to all background patterns here.
Source V. Hartikainen
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
Super detailed 16×16 tile that forms a beautiful pattern of straws.
Source Pavel
From a drawing in 'Two Women in the Klondike', Mary Hitchcock, 1899.
Source Firkin
There are many carbon patterns, but this one is tiny.
Source Designova
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin