A nice one indeed, but I have a feeling we have it already? If you spot a copy, let me know on Twitter.
Source Graphiste
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Same classic 45-degree pattern, dark version.
Source Luke McDonald
Remixed from a drawing in 'Jezebel's Daughter', Wilkie Collins 1880
Source Firkin
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Zero CC tileable moss or lichen covered stone texture, edited from pixabay. CC0
Source Sojan Janso
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
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
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
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
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 very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
A seamless web background with texture of aged grid paper.
Source V. Hartikainen
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic