A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
Looks as if it's spray painted on the wall. You can be sure that this pattern will seamlessly fill your backgrounds on web pages.
Source V. Hartikainen
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Geometric Pattern Background
Source GDJ
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Inspired by a 1930s wallpaper pattern I saw on TV.
Source Firkin
The image depicts a seamless pattern made using a bird's face.
Source Yamachem
So tiny, just 7 by 7 pixels – but still so sexy. Ah yes.
Source Dmitriy Prodchenko
It’s like Shine Dotted’s sister, only rotated 45 degrees.
Source mediumidee
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Black & white version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Prismatic Basic Pattern 2 No Background
Source GDJ
From a drawing in 'La Principauté de Liège et les Pays-Bas au XVIe siècle', Société des Bibliophiles Liégeois ,1887.
Source Firkin
A seamless pattern formed from background pattern 102
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'Jardyne's Wife', Charles Wills, 1891.
Source Firkin
Green Background Pattern
Source V. Hartikainen
This could be a hippy vintage wallpaper.
Source Tileable Patterns