This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
One more brick pattern. A bit more depth to this one.
Source Benjamin Ward
A dark pattern made out of 3×3 circles and a 1px shadow. This works well as a carbon texture or background.
Source Atle Mo
From a drawing in 'A Life Interest', Mrs Alexander, 1888.
Source Firkin
Geometric triangles seem to be quite hot these days.
Source Pixeden
Zero CC tileable grass texture, photographed and made by me. CC0
Source Sojan Janso
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
Remixed from a drawing in 'Incidents on a Journey through Nubia to Darfoor', F. Ensor, 1891.
Source Firkin
A bit strange this one, but nice at the same time.
Source Diogo Silva
Derived from an image that was uploaded to Pixabay by mdmelo.
Source Firkin
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Prismatic Geometric Pattern Background 2
Source GDJ
A white version of the very popular linen pattern.
Source Ant Ekşiler
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova