Might not be super subtle, but quite original in its form.
Source Alex Smith
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless pattern with green and yellow diagonal lines on top of a white dotted background.
Source V. Hartikainen
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Zero CC tileable brick texture, photographed and made by me. CC0
Source Sojan Janso
Remixed from a drawing that was uploaded to Pixabay by captenpub.
Source Firkin
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
Prismatic Abstract Background Design
Source GDJ
An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
ZeroCC tileable beechwood wood texture, generated in Neo Texture Edit by me. CC0
Source Sojan Janso
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
From a drawing in 'La Principauté de Liège et les Pays-Bas au XVIe siècle', Société des Bibliophiles Liégeois ,1887.
Source Firkin
Retro Circles Background 7 No Black
Source GDJ
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A very slick dark rubber grip pattern, sort of like the grip on a camera.
Source Sinisha