A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
You know I love paper patterns. Here is one from Stephen. Say thank you!
Source Stephen Gilbert
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
Formed by distorting an image on Pixabay that was uploaded by gustavorezende. To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a drawing in 'Bond Slaves. The story of a struggle.', Isabella Varley, 1893.
Source Firkin
Abstract Stars Geometric Pattern Prismatic No Background
Source GDJ
An alternative colour scheme for the original background.
Source Firkin
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
There are many carbon patterns, but this one is tiny.
Source Designova
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
One more sharp little tile for you. Subtle circles this time.
Source Blunia
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
Prismatic Floral Pattern 3 Variation 3 No Background
Source GDJ
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
A pale yellow background pattern with vertical stripes. The stripes are partially faded. I think this background image turned out pretty well, especially those faded stripes.
Source V. Hartikainen
Remixed from an image that was uploaded to Pixabay by CatherineClennan
Source Firkin