A seamless design of flowers remixed from a jpg on Pixabay by Prawny.
Source Firkin
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
Formed by distorting an image on Pixabay that was uploaded by gustavorezende. To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
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
Prismatic Hexagonalism Pattern No Background
Source GDJ
Inspired by a JPG that was uploaded to Pixabay by kokon_art
Source Firkin
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
The perfect pattern for all your blogs about type, or type-related matters.
Source Atle Mo
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.
Source Lazur URH
Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae