A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
Zero CC tileable pine bark texture, photographed and made by me. CC0
Source Sojan Janso
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a drawing in 'Bond Slaves. The story of a struggle.', Isabella Varley, 1893.
Source Firkin
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
Colored maple leaves scattered on a surface. This is tileable, so it can be used as a background or wallpaper.
Source Eady
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
A pattern formed from repeated instances of corner decoration 8. To get the basic tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
A version without colours blended together to give a different look.
Source Firkin
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Feel free to download this "Dark Wood" background texture for your web site. The background tiles seamlessly!
Source V. Hartikainen
This seamless pattern consists of a blue grid on a yellow background.
Source V. Hartikainen
A set of paper filters. The base texture is generated the same way, only the compositing mode is varied.
Source Lazur URH
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight