Inspired by this, I came up with this pattern. Madness!
Source Atle Mo
A rusty grunge background for websites. Feel free to use it in your site's theme.
Source V. Hartikainen
Prismatic Polka Dots Mark II No Background
Source GDJ
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Seamless Olive Green Web Background Image
Source V. Hartikainen
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Light and tiny, just the way you like it.
Source Rohit Arun Rao
To get the repeating unit, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
Same classic 45-degree pattern, dark version.
Source Luke McDonald
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Number 4 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
This one looks like a cork panel. Feel free to use it as a tiled background on your blog or website.
Source V. Hartikainen
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A fun-looking elastoplast/band-aid pattern. A hint of orange tone in this one.
Source Josh Green
High detail stone wall with minor cracks and specks.
Source Projecteightyfive