The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Nasty or not, it’s a nice pattern that tiles. Like they all do.
Source Badhon Ebrahim
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Seamless pattern formed from a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
Subtle scratches on a light gray background.
Source Andrey Ovcharov
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Classy golf-pants pattern, or crossed stripes if you will.
Source Will Monson
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
It’s like Shine Dotted’s sister, only rotated 45 degrees.
Source mediumidee
I skipped number 3, because it wasn’t all that great. Sorry.
Source Dima Shiper
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
A free light orange brown wallpaper with vertical stripes designed for use as a tiled background on websites. An yet another background pattern with vertical stripes.
Source V. Hartikainen
Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Tiny little flowers growing on your screen. Nice, huh?
Source Themes Tube
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin