Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Prismatic Groovy Concentric Background 3
Source GDJ
The tile can be had by using shift+alt+i on the selected rectangle in Inkscape
Source Firkin
A version without colours blended together to give a different look.
Source Firkin
A background pattern with blue on white vertical stripes.
Source V. Hartikainen
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Little x’es, noise and all the stuff you like. Dark like a Monday, with a hint of blue.
Source Tom McArdle
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Paper model of a tetrahedron. Modelo de papel de um tetraedro.
Source laobc
A bit of scratched up grayness. Always good.
Source Dmitry
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Here's a new gray "fabric" pattern. Use it as backgrounds for websites or for other purposes.
Source V. Hartikainen
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
The image is the remix of "wire-mesh fence seamless pattern" .This is a more minute version of it.Sorry for the file size.Using path>difference in Inkscape, I will cut out any silhouette from this pattern and create a "meshed silhouette".
Source Yamachem
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i
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
I love these crisp, tiny, super subtle patterns.
Source Badhon Ebrahim
From a drawing in 'Danmarks Riges Historie af J. Steenstrup, Kr. Erslev, A. Heise, V. Mollerup, J. A. Fridericia, E. Holm, A. D. Jørgensen', 1897.
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen