This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
This one has rusty dark brown texture.
Source V. Hartikainen
This is a seamless pattern which is derived from a flower petal image.
Source Yamachem
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Looks like an old rug or a computer chip.
Source Patutin Sergey
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Seamless Olive Green Web Background Image
Source V. Hartikainen
An alternative colour scheme for the original seamless texture formed from an image on Pixabay.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Little x’es, noise and all the stuff you like. Dark like a Monday, with a hint of blue.
Source Tom McArdle
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
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
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A repeating background for websites with a texture of black groove stripes.
Source V. Hartikainen
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Classic vertical lines, in all its subtlety.
Source Cody L
Prismatic Polka Dots Mark II No Background
Source GDJ
Prismatic Geometric Pattern Background No Black
Source GDJ