The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A bit simplified version. Although it could be edited out to be simpler. Anyway, this time the tiling is converted to a pattern fill -which is using clipping for the tile's edges.
Source Lazur URH
A free web background image with a seamless concrete-like texture and an Indian-red color.
Source V. Hartikainen
Vertical lines with a bumpy, yet crisp, feel to it.
Source Raasa
A free grid paper background pattern for using on web sites.
Source V. Hartikainen
Here's a brown background pattern with subtle stripes. I hope you'll like the color. If not, feel free to change it using an image editor, if you know how of course. Personally, I'm using GIMP to create these backgrounds.
Source V. Hartikainen
More in the paper realm, this time with fibers.
Source Jorge Fuentes
Colourful background achieved with gradient fills.
Source Firkin
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
A very dark asfalt pattern based off of a photo taken with my iPhone.
Source Atle Mo
This makes me wanna shoot some pool! Sweet green pool table pattern.
Source Caveman
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
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
So tiny, just 7 by 7 pixels – but still so sexy. Ah yes.
Source Dmitriy Prodchenko
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
From a drawing in 'A Life Interest', Mrs Alexander, 1888.
Source Firkin