Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
The image depicts a seamless pattern of Japanese Edo pattern called "kikkou-matsu" or "亀甲松" meaning " tortoiseshell-pinetree".The real pinetree is like this: https://jp.pinterest.com/pin/500744052301065077/
Source Yamachem
A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.
Source Dima Shiper
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Remixed from a raster on Pixabay, that was uploaded by ArtsyBee.
Source Firkin
A new take on the black linen pattern. Softer this time.
Source Atle Mo
This light yellow background pattern consists of an irregular pattern of spots. Here's a light background pattern with yellowish tint.
Source V. Hartikainen
A seamless pattern recreated from an image on Pixabay. It is reminiscent of parquet flooring and is formed from a square tile, which can be recovered in Inkscape by selecting the ungrouped rectangle and using shift-alt-I together.
Source Firkin
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
Vector version of a JPG that was uploaded to Pixabay by theasad121
Source Firkin
No idea what Nistri means, but it’s a crisp little pattern nonetheless.
Source Markus Reiter
Nice little grid. Would work great as a base on top of some other patterns.
Source Arno Gregorian
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
The tile can be had by selecting the rectangle in Inkscape and using shift+alt+i. Remixed from a drawing in 'Flowers of Song', Frederick Weatherly, 1895.
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
This background pattern has futuristic look. So, maybe it could be used on websites or blogs dedicated to video games?!
Source V. Hartikainen
A background tile of dark textile. Made this a long time ago and just now decided to publish it.
Source V. Hartikainen
This is sort of fresh, but still feels a bit old school.
Source Martuchox