CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
Subtle scratches on a light gray background.
Source Andrey Ovcharov
New paper pattern with a slightly organic feel to it, using some thin threads.
Source Atle Mo
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
Prismatic Hexagonalist Pattern No Background
Source GDJ
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
I’m not going to use the word Retina for all the new patterns, but it just felt right for this one. Huge wood pattern for ya’ll.
Source Atle Mo
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin
Zero CC tileable pine bark texture, photographed and made by me. CC0
Source Sojan Janso
Prismatic Hypnotic Pattern No Background
Source GDJ
Black brick wall pattern. Brick your site up!
Source Alex Parker
Plywood Web Background background image for use in web design.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Seamless Prismatic Quadrilateral Line Art Pattern No Background
Source GDJ
Zero CC tileable wood texture, made by me procedurally in Neo Texture Edit.
Source Sojan Janso
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
A seamless light gray paper texture with horizontal double lines.
Source V. Hartikainen
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
Here's a dark background pattern that contains a steel grid pattern as a texture. Use it as a website background or for other purposes. It's free!
Source V. Hartikainen
Farmer could be some sort of fabric pattern, with a hint of green.
Source Fabian Schultz