From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
A cute x, if you need that sort of thing.
Source Juan Scrocchi
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
The Grid. A digital frontier. I tried to picture clusters of information as they traveled through the computer.
Source Haris Šumić
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A rusty grunge background for websites. Feel free to use it in your site's theme.
Source V. Hartikainen
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
Continuing the geometric trend, here is one more.
Source Mike Warner
A large pattern with funky shapes and form. An original. Sort of origami-ish.
Source Luuk van Baars
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
From an image on opengameart.org shared by rubberduck.
Source Firkin
U.S.-based National Fire Protection Association standard fire diamond for flagging risks posed by hazardous materials. The red diamond has a number 0-4 depending on flammability. The blue diamond has a number 0-4 depending on health hazard. The yellow has a number 0-4 depending on reactivity. the white square has a special notice, e.g OX for oxidizer.
Source Firkin
A bit strange this one, but nice at the same time.
Source Diogo Silva
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
Tiny circle waves, almost like the ocean.
Source Sagive
Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry