A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Prismatic Polka Dots 3 No Background
Source GDJ
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
Prismatic Geometric Pattern Background No Black
Source GDJ
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Small dots with minor circles spread across to form a nice mosaic.
Source John Burks
This makes me wanna shoot some pool! Sweet green pool table pattern.
Source Caveman
The name is totally random, but hey, it sounds good.
Source Atle Mo
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use 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
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Black brick wall pattern. Brick your site up!
Source Alex Parker
A rusty grunge background for websites. Feel free to use it in your site's theme.
Source V. Hartikainen