Remixed from an image that was uploaded to Pixabay by CatherineClennan
Source Firkin
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
Thin lines, noise and texture creates this crisp dark denim pattern.
Source Marco Slooten
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
Prismatic Polka Dots 3 No Background
Source GDJ
This beige background pattern resembles a concrete wall with engravings or something similar to it.
Source V. Hartikainen
The classic notebook paper with horizontal stripes.
Source Are Sundnes
A repeating graphic with ancient pattern. I came up with this name/title at last minute, so you may find that there is very little of ancientness in this pattern after all.
Source V. Hartikainen
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Black version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
The image is a seamless pattern of a fishnet.
Source Yamachem
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
Prismatic Abstract Geometric Background 5
Source GDJ
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
Fake or not, it’s quite luxurious.
Source Factorio.us Collective
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin
Here's an yet another background for websites, with a seamless texture of wood planks this time.
Source V. Hartikainen
Prismatic Abstract Line Art Pattern Background 2
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
Inspired by a design found in 'Konstantinápolyi emlékeim', Miklos Chriszto, 1893.
Source Firkin
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin