CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Lovely pattern with some good-looking non-random noise lines.
Source Zucx
I love cream! 50x50px and lovely in all the good ways.
Source Thomas Myrman
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
From a drawing in 'Cassell's Library of English Literature', Henry Morley, 1883.
Source Firkin
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
A seamless design of flowers remixed from a jpg on Pixabay by Prawny.
Source Firkin
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
From a drawing in 'Handbook of the excursions proposed to be made by the Lincoln Diocesan Architectural Society, on the 27th and 28th of May, 1857', Edward Trollope, 1857.
Source Firkin
Fake or not, it’s quite luxurious.
Source Factorio.us Collective
An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
This background has abstract texture with some similarities to wood.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
A free background pattern with abstract green tiles.
Source V. Hartikainen
Colour version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin