Sometimes you just need the simplest thing.
Source Fabricio
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
Prismatic Basic Pattern 2 No Background
Source GDJ
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Same classic 45-degree pattern, dark version.
Source Luke McDonald
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Luxury pattern, looking like it came right out of Paris.
Source Daniel Beaton
This was formed by distorting an image of a background on Pixabay.
Source Firkin
I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
I love cream! 50x50px and lovely in all the good ways.
Source Thomas Myrman
Inspired by a design found in 'Konstantinápolyi emlékeim', Miklos Chriszto, 1893.
Source Firkin
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
Derived from a corner decoration itself found as a jpg on Pixabay.
Source Firkin
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Prismatic Groovy Concentric Background
Source GDJ