Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A background pattern with green vertical stripes. A new striped background pattern. This time a green one.
Source V. Hartikainen
A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
From a drawing in 'A Rolling Stone. A tale of wrongs and revenge', John Hartley, 1878.
Source Firkin
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Here I have tried to create something that would look like maple wood. Not sure how well it's turned out, but at least it looks like wood.
Source V. Hartikainen
Inspired by this, I came up with this pattern. Madness!
Source Atle Mo
No, not the band but the pattern. Simple squares in gray tones, of course.
Source Atle Mo
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss