A dark pattern made out of 3×3 circles and a 1px shadow. This works well as a carbon texture or background.
Source Atle Mo
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
This could be a hippy vintage wallpaper.
Source Tileable Patterns
Inspired by a 1930s wallpaper pattern I saw on TV.
Source Firkin
Prismatic Geometric Pattern Background
Source GDJ
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo
Remixed from a raster on Pixabay that was uploaded by ArtsyBee.
Source Firkin
Dark Tile-able Grunge Texture. I think this texture can be classified as grunge. It's free and seamless, as always.
Source V. Hartikainen
Inspired by this, I came up with this pattern. Madness!
Source Atle Mo
Seamless tile drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
A gray background pattern with a texture of textile. Suits perfectly for web design.
Source V. Hartikainen
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Prismatic Groovy Concentric Background No Black
Source GDJ
A seamless background texture of old cardboard.
Source V. Hartikainen
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
These dots are already worn for you, so you don’t have to.
Source Matt McDaniel
Prismatic Abstract Line Art Pattern Background
Source GDJ
Zero CC tileable wood texture, made by me procedurally in Neo Texture Edit.
Source Sojan Janso
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin