Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Classy golf-pants pattern, or crossed stripes if you will.
Source Will Monson
Abstract Stars Geometric Pattern Prismatic No Background
Source GDJ
Subtle scratches on a light gray background.
Source Andrey Ovcharov
From a drawing in 'Codogno e il suo territorio nella cronaca e nella storia'', Gio and Giarella Cairo, 1897.
Source Firkin
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Alternative colour scheme for the original floral pattern.
Source Firkin
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo
Heavily remixed from a drawing in 'Barbara Leybourne; a story of eighty years ago', Sarah Hamer, 1889.
Source Firkin
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Lovely light gray floral motif with some subtle shades.
Source GraphicsWall
A bit of scratched up grayness. Always good.
Source Dmitry
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Turn your site into a dragon with this great scale pattern.
Source Alex Parker
The tile can be had by using shift+alt+i on the selected rectangle in Inkscape
Source Firkin
CC0 and seamless wellington boot pattern.
Source SliverKnight
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
A pattern formed from repeated instances of corner decoration 8. To get the basic tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i
Source Firkin
A brown metallic grid pattern layered on top of a dark fabric texture. It should look great when using as a tiled background on web pages, especially blogs.
Source V. Hartikainen
Non-seamless pattern drawn in Paint.net and vectorised in Vector Magic.
Source Firkin