A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
Dark blue concrete wall with some small dust spots.
Source Atle Mo
Seamless pattern the basic tile for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
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 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Might not be super subtle, but quite original in its form.
Source Alex Smith
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
I asked Gjermund if he could make a pattern for us – result!
Source Gjermund Gustavsen
Prismatic Groovy Concentric Background 5
Source GDJ
Like the name suggests, this background image consists of a pattern of dark bricks. It may be an option for you, if you are looking for something that looks like a brick wall for use as a background on web pages. It's not a masterpiece, but looks pretty nice when is tiled.
Source V. Hartikainen
Inspired by a pattern found 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
A seamless background colored in pale orange. It has a paper like texture with diagonal grid pattern.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
The name alone is awesome, but so is this sweet dark pattern.
Source Federica Pelzel
A repeating background of beige paper with vintage look. Repeats to infinity, as usual.
Source V. Hartikainen
Lovely pattern with some good-looking non-random noise lines.
Source Zucx
Seamless Prismatic Quadrilateral Line Art Pattern No Background
Source GDJ
Zero CC tileable pine bark texture, photographed and made by me. CC0
Source Sojan Janso
Did anyone say The Hoff? This pattern is in no way related to Baywatch.
Source Josh Green
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
There are many carbon patterns, but this one is tiny.
Source Designova
Black & white version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin