Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen
This light blue background pattern is quite pleasing to the eye, it consists of a tiny rough grid pattern, which is seamless by design. That's it, if you like the color, you can use this seamless pattern in a web design without making any further modifications to it.
Source V. Hartikainen
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.
Source Firkin
A seamless texture of a rough concrete surface.
Source V. Hartikainen
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
Remixed from a JPG that was uploaded to Pixabay by theasad121
Source Firkin
A seamless texture of black leather. I think it will look best when used in headers, footers or sidebars.
Source V. Hartikainen
Seamless Light Background Texture.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
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. Version with black background.
Source Firkin
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
8 by 8 pixels, and just what the title says.
Source pixilated
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
The image depicts polka dot seamless pattern.
Source Yamachem
From a drawing in 'Bond Slaves. The story of a struggle.', Isabella Varley, 1893.
Source Firkin
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo
This is so subtle you need to bring your magnifier!
Source Carlos Valdez