A free black metallic background pattern. Here's a new pattern I made that looks metallic.
Source V. Hartikainen
Same classic 45-degree pattern, dark version.
Source Luke McDonald
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
Colour version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
One more updated pattern. Not really carbon fiber, but it’s the most popular pattern, so I’ll give you an extra choice.
Source Atle Mo
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
The classic notebook paper with horizontal stripes.
Source Are Sundnes
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Prismatic Hypnotic Pattern 2 No Background
Source GDJ
Black version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
By popular request, an outline version of the pentagon pattern.
Source Atle Mo
Retro Circles Background 8 No Black
Source GDJ