A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
A nice one indeed, but I have a feeling we have it already? If you spot a copy, let me know on Twitter.
Source Graphiste
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Here's a new paper-like background for free use on personal and commercial projects (this applies to all background patterns here).
Source V. Hartikainen
It’s an egg, in the form of a pattern. This really is 2012.
Source Paul Phönixweiß
Utilising a bird from s-light and some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
This one needs to be used in small areas; you can see it repeat.
Source Luca
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts
Prismatic Geometric Pattern Background No Black
Source GDJ
Greyscale version of a pattern that came out of playing with the 'slinky' plug-in for Paint.net
Source Firkin
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Hypnotic Pattern No Background
Source GDJ
Seamless pattern made from a tile that can be obtained in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A seamless pattern the unit cell for which 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