Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
A tile-able background for websites with paper-like texture and a grid pattern layered on top of it.
Source V. Hartikainen
Prismatic Triangular Seamless Pattern III With Background
Source GDJ
Not even 1kb, but very stylish. Gray thin lines.
Source Struck Axiom
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki
Pattern Background, Texture, Photoshop Structure style CC0 texture.
Source Darkmoon1968
I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
Here's a brown background pattern with subtle stripes. I hope you'll like the color. If not, feel free to change it using an image editor, if you know how of course. Personally, I'm using GIMP to create these backgrounds.
Source V. Hartikainen
This light yellow background pattern consists of an irregular pattern of spots. Here's a light background pattern with yellowish tint.
Source V. Hartikainen
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using 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 moss or lichen covered stone texture, edited from pixabay. CC0
Source Sojan Janso
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
A bit simplified version. Although it could be edited out to be simpler. Anyway, this time the tiling is converted to a pattern fill -which is using clipping for the tile's edges.
Source Lazur URH
ZeroCC tileable mossy (lichen) stone texture, edited from pixabay. CC0
Source Sojan Janso
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use 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
From a drawing in 'From Snowdon to the Sea. Striking stories of North and South Wales', Marie Trevelyan, 1895.
Source Firkin
One can never have too few rice paper patterns, so here is one more.
Source Atle Mo
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin