The tile for this is based on a repeating unit close to a design on Pixabay. It can be had by selecting the rectangle in Inkscape and using 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
Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Kaleidoscope Prismatic Abstract No Background
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
This pattern comes in orange, and it looks as if it is "made of glass".
Source V. Hartikainen
The classic notebook paper with horizontal stripes.
Source Are Sundnes
Little x’es, noise and all the stuff you like. Dark like a Monday, with a hint of blue.
Source Tom McArdle
A version without colours blended together to give a different look.
Source Firkin
The image is a seamless pattern of a fishnet.
Source Yamachem
Prismatic Abstract Geometric Background 5 No Black
Source GDJ
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Remixed from a drawing in 'Prehistoric Man: researches into the origin of civilisation in the old and the new world', Daniel Wilson, 1876.
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.
Source Firkin
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
I love cream! 50x50px and lovely in all the good ways.
Source Thomas Myrman
First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.
Source Atle Mo
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec