Not so subtle. These tileable wood patterns are very useful.
Source Elemis
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
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
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
This makes me wanna shoot some pool! Sweet green pool table pattern.
Source Caveman
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
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
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
Plywood Web Background background image for use in web design.
Source V. Hartikainen
Zero CC tileable Crackled Cement (streaks) texture, photographed and made by me. CC0
Source Sojan Janso
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Prismatic Polka Dots Mark II No Background
Source GDJ
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
An abstract pale yellow paper-like background with stains colored in yellow and green.
Source V. Hartikainen
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Zero CC Mossy stone tileable texture, photographed and made by me. CC0
Source Sojan Janso
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
I love these crisp, tiny, super subtle patterns.
Source Badhon Ebrahim
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Colour version of the original pattern inspired by the front cover of 'Old and New Paris', Henry Edwards, 1894.
Source Firkin
Prismatic Polka Dots Mark II 3 No Background
Source GDJ
This was formed by distorting an image of a background on Pixabay.
Source Firkin