Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Inspired by a drawing in 'Poems', James Smith, 1881.
Source Firkin
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
Remixed from an image on Pixabay uploaded by Prawny
Source Firkin
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
This background has abstract texture with some similarities to wood.
Source V. Hartikainen