Might not be super subtle, but quite original in its form.
Source Alex Smith
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
Remixed from a drawing in 'A Girl in Ten Thousand', Elizabeth Meade, 1896.
Source Firkin
Zero CC asphalt, pavement, texture, photographed and made by me. CC0 WARNING I FOUND A SEAM ON THIS TEXTURE
Source Sojan Janso
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
Found on the ground in french cafe in kunming, Yunnan, china
Source Rejon
On a large canvas you can see it tiling, but used on smaller areas, it’s beautiful.
Source Paul Phönixweiß
From a drawing in 'Hundert Jahre in Wort und Bild', S. Stefan, 1899.
Source Firkin
Derived from a JPG that was uploaded to Pixabay by ractapopulous
Source Firkin
A bit strange this one, but nice at the same time.
Source Diogo Silva
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Abstract Tiled Background Extended 8
Source GDJ
Prismatic Groovy Concentric Background No Black
Source GDJ
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
Green Background Pattern
Source V. Hartikainen
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
White circles connecting on a light gray background.
Source Mark Collins