A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
Formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'Bond Slaves. The story of a struggle.', Isabella Varley, 1893.
Source Firkin
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
Prismatic Polka Dots Mark II 2 No Background
Source GDJ
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I. A version of the original with random colors.
Source Firkin
A pattern derived from repeating unit cells each derived from part of a mosaic in paint.net. The starting point for the mosaic was a picture of some prawns!
Source Firkin
A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
An alternative colour scheme to the original seamless pattern.
Source Firkin
A bit of scratched up grayness. Always good.
Source Dmitry
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From a drawing in 'Cassell's Library of English Literature', Henry Morley, 1883.
Source Firkin
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
Nothing like a clean set of bed sheets, huh?
Source Badhon Ebrahim
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
A free background tile with a pattern of pink bump dots. This background tile is sweet! Moreover, it's designed for use as website backgrounds.
Source V. Hartikainen
You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova