This one is amazing, truly original. Go use it!
Source Viahorizon
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
A dark brown fabric-like background texture with seamless pattern of winding stripes.
Source V. Hartikainen
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Neat little photography icon pattern.
Source Hossam Elbialy
Black brick wall pattern. Brick your site up!
Source Alex Parker
Tweed is back in style – you heard it here first. Also, the @2X version here is great!
Source Simon Leo
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
You may use it as is, or modify it as you like.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
This one needs to be used in small areas; you can see it repeat.
Source Luca
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
One can never have too few rice paper patterns, so here is one more.
Source Atle Mo
A free seamless background with pink spots.
Source V. Hartikainen
An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
Derived from an image that was uploaded to Pixabay by darkmoon1968
Source Firkin
A free background pattern with abstract green tiles.
Source V. Hartikainen
Black version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Gold Triangular Seamless Pattern No Background
Source GDJ
Prismatic Groovy Concentric Background 3
Source GDJ