This is the third pattern called Dark Denim, but hey, we all love them!
Source Brandon Jacoby
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
Prismatic Abstract Geometric Background derived from an image on Pixabay.
Source GDJ
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova
A pattern formed from repeated instances of corner decoration 8. To get the basic tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
A floral background formed from numerous clones of flower 117.
Source Firkin
From drawing in 'Musings in Maoriland', Thomas Bracken, 1890.
Source Firkin
Colourful background achieved with gradient fills.
Source Firkin
Prismatic Triangular Seamless Pattern III With Background
Source GDJ
A free background pattern with abstract green tiles.
Source V. Hartikainen
It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
Thin lines, noise and texture creates this crisp dark denim pattern.
Source Marco Slooten
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Prismatic Geometric Pattern Background 2 No Black
Source GDJ
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
More in the paper realm, this time with fibers.
Source Jorge Fuentes
The Grid. A digital frontier. I tried to picture clusters of information as they traveled through the computer.
Source Haris Šumić
Psychedelic Geometric Background No Black
Source GDJ