This seamless pattern consists of a blue grid on a yellow background.
Source V. Hartikainen
This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
Prismatic Floral Background No Black
Source GDJ
A repeating gloomy background image. This one consists of a pattern of black chains layered on top of a dark textured background.
Source V. Hartikainen
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
Might not be super subtle, but quite original in its form.
Source Alex Smith
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
From a drawing in 'A Rolling Stone. A tale of wrongs and revenge', John Hartley, 1878.
Source Firkin
Fix and cc0 to get the tile this is based on.
Source SliverKnight
Remixed from a PNG that was uploaded to Pixabay by gingertea
Source Firkin
Classic vertical lines, in all its subtlety.
Source Cody L
Subtle scratches on a light gray background.
Source Andrey Ovcharov
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Actually remixed from a pattern on Pixabay. But then noticed a very similar one on Openclipart.org uploaded by btj51q2.
Source Firkin
Inspired by a JPG that was uploaded to Pixabay by kokon_art
Source Firkin
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
Light gray paper pattern with small traces of fiber and some dust.
Source Atle Mo
This one has rusty dark brown texture.
Source V. Hartikainen
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo