Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
Turn your site into a dragon with this great scale pattern.
Source Alex Parker
Classy golf-pants pattern, or crossed stripes if you will.
Source Will Monson
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless pattern formed from a modified version of rwwgub's tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
Same classic 45-degree pattern, dark version.
Source Luke McDonald
Seamless Green Tile Background
Source V. Hartikainen
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
Formed from decorative divider 184 in paint.net. Vectorised with Vector Magic.
Source Firkin
As the original image 's page size is too large for its image size, I remixed it.
Source Yamachem
You guessed it – looks a bit like cloth.
Source Peax Webdesign
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
ZeroCC tileable wood boards texture, photographed and made by me. CC0
Source Sojan Janso
Derived from an image that was uploaded to Pixabay by darkmoon1968
Source Firkin
A comeback for you: the popular Escheresque, now in black.
Source Patten
An orange vertically striped background pattern. Feel free to download and use this orange background pattern, for example, on the web). It resembles a wallpaper with vertical stripes or something similar to it.
Source V. Hartikainen
This one is amazing, truly original. Go use it!
Source Viahorizon
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin