People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Dark pattern with some nice diagonal stitched lines crossing over.
Source Ashton
A blue gray fabric-like texture for websites. An yet another fabric-like texture. It has subtle vertical and diagonal stripes to it.
Source V. Hartikainen
Textured Red Brown Plastic, Free Background Pattern. Although there's already enough plastic in our lives, let's bring it to the web too.)
Source V. Hartikainen
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
Seamless Prismatic Quadrilateral Line Art Pattern No Background
Source GDJ
This background texture resembles stone. It may be used as a background on web pages or on some of their html elements (header, borders, menu bar, etc.). Just modify it for your needs.
Source V. Hartikainen
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Curved Diamond Pattern 7 No Background
Source GDJ
This was submitted in a beige color, hence the name. Now it’s a gray paper pattern.
Source Konstantin Ivanov
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin