A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
You know you can’t get enough of these linen-fabric-y patterns.
Source James Basoo
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
This background image has seamless texture that resembles a surface of gray stone.
Source V. Hartikainen
Prismatic Groovy Concentric Background 5 No Black
Source GDJ
A criss-cross pattern similar to one I saw mown into a sports field.
Source Firkin
This background pattern contains a seamless texture of bark. It's not very realistic, but I think it looks quite nice.
Source V. Hartikainen
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A seamless tessellation pattern. To get the tile this is formed from, select the pattern in Inkscape and use shift+alt+i.
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
An attempt for cleaning up the original image in a few steps.
Source Lazur URH
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
Seamless Prismatic Geometric Pattern With Background
Source GDJ
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin