Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
A seamless background pattern with impressed gray dots.
Source V. Hartikainen
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
Tiny little flowers growing on your screen. Nice, huh?
Source Themes Tube
I’m not going to use the word Retina for all the new patterns, but it just felt right for this one. Huge wood pattern for ya’ll.
Source Atle Mo
Prismatic Hypnotic Pattern No Background
Source GDJ
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Remixed from a raster on Pixabay that was uploaded by ArtsyBee.
Source Firkin
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
Zero CC tileable dry grass texture, photographed and made by me. CC0
Source Sojan Janso
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
A nice and simple white rotated tile pattern.
Source Another One
Feel free to download this "Dark Wood" background texture for your web site. The background tiles seamlessly!
Source V. Hartikainen