A heavy hitter at 400x400px, but lovely still.
Source Breezi
Embossed lines and squares with subtle highlights.
Source Alex Parker
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
This ons is quite old school looking. Retro, even. I like it.
Source Arno Declercq
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
This ladies and gentlemen, is texturetastic! Love it.
Source Adam Pickering
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
A pattern derived from part of a fractal rendering in Paint.net.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
Prismatic Polka Dots 3 No Background
Source GDJ
Remixed from a drawing in 'Line and form", Walter Crane, 1914.
Source Firkin