Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Feel free to download this "Dark Wood" background texture for your web site. The background tiles seamlessly!
Source V. Hartikainen
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
Love me some light mesh on a Monday. Sharp.
Source Wilmotte Bastien
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
A repeating background of beige (or is it more vanilla yellow) textured stripes. One more background with stripes.
Source V. Hartikainen
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless pattern formed from a tile made from ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Retro Circles Background 8 No Black
Source GDJ
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Prismatic Hexagonalism Pattern No Background
Source GDJ
From a drawing in 'Cassell's Library of English Literature', Henry Morley, 1883.
Source Firkin
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
Derived from an image that was uploaded to Pixabay by starchim01
Source Firkin