Dark Denim #372
 Dark  CC BY-SA 3.0

Thin lines, noise and texture creates this crisp dark denim pattern.

Source Marco Slooten

 More Textures
Abstract Tiled Background Extended 11 #522
 Noise  CC 0

Abstract Tiled Background Extended 11

Source GDJ

Pattern cleanup 4 #157
 Noise  CC 0

An attempt for cleaning up the original image in a few steps.

Source Lazur URH

Background pattern 226 (colour 4) #2319
 Green  CC 0

A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.

Source Firkin

Prismatic Abstract Line Art Pattern Background 2@2X #568
 Dark  CC 0

Prismatic Abstract Line Art Pattern Background 2

Source GDJ

Dark Brick Wall@2X #136
 Wall  CC BY-SA 3.0

Black brick wall pattern. Brick your site up!

Source Alex Parker

Wood #49
 Wood  CC BY-SA 3.0

Dark wooden pattern, given the subtle treatment. based on texture from Cloaks.

Source Atle Mo
Based from Cloaks

Carbon Fiber v2 #105
 Carbon  CC BY-SA 3.0

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

“Transparent” Background Pattern@2X #494
 Light  CC 0

An emulated “transparent” background pattern, like that of all kinds of computer graphics software.

Source AdamStanislav

Background pattern 8 (greyscale) #210
 Dark  CC 0

Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net

Source Firkin

Paper 2@2X #22
 Paper  CC BY-SA 3.0

New paper pattern with a slightly organic feel to it, using some thin threads.

Source Atle Mo

Fish Pattern Background #233
 Noise  CC 0

From PDP.

Source GDJ

Background pattern 6 #225
 Noise  CC 0

Another fairly simple design drawn in Paint.net and vectorized in Inkscape.

Source Firkin

Background pattern 270 #2061
 Dark  CC 0

A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin