A repeating background of thick textured paper. Actually, it turned out to look like something between a paper and fabric.
Source V. Hartikainen
Classy golf-pants pattern, or crossed stripes if you will.
Source Will Monson
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Derived from a corner decoration itself found as a jpg on Pixabay.
Source Firkin
Zero CC asphalt, pavement, texture, photographed and made by me. CC0 WARNING I FOUND A SEAM ON THIS TEXTURE
Source Sojan Janso
Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
A repeating background of beige (or is it more vanilla yellow) textured stripes. One more background with stripes.
Source V. Hartikainen
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
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
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Stefan is hard at work, this time with a funky pattern of squares.
Source Stefan Aleksić
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
This light background pattern has a texture of "frozen" surface with diagonal stripes. Here's an yet another addition to the collection of free website backgrounds.
Source V. Hartikainen
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Seamless SVG vector and JPG backgrounds with faded diagonal stripes. The colors are editable.
Source V. Hartikainen
Free tiled background with colorful stripes and white splatter.
Source V. Hartikainen