The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
A seamless web background with texture of aged grid paper.
Source V. Hartikainen
This metal background pattern resembles a metal plate with rivets. Solid rivets on a metal plate.
Source V. Hartikainen
A light brushed aluminum pattern for your pleasure.
Source Tim Ward
The tile this is based on was adapted from an image that was uploaded to Pixabay by frolicsomepl. It can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Produced using the clouds, flames and glass blocks plug-ins in Paint.net and the resulting .PNG vectorised with Vector Magic.
Source Firkin
This one is super crisp at 2X. Lined paper with some dust and scratches.
Source HQvectors
A version without colours blended together to give a different look.
Source Firkin
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Prismatic Hypnotic Pattern No Background
Source GDJ
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
An attempt for cleaning up the original image in a few steps.
Source Lazur URH
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Same as Silver Scales, but in black. Turn your site into a dragon with this great scale pattern.
Source Alex Parker