Submitted as a black pattern, I made it light and a few steps more subtle.
Source Andy
Uses spirals from Pixabay. To get the basic tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
This one is quite simple in design, it consists of vertical stripes layered on top of a seamless texture.
Source V. Hartikainen
The image is a seamless pattern which is derived from a vine .Consequently, the vine got like dots via vectorization.The original vine is here:jp.pinterest.com/pin/500744052301410188/
Source Yamachem
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using 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
Sometimes you just need the simplest thing.
Source Fabricio
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
An abstract texture of black metal pipes (seamless).
Source V. Hartikainen
Zero CC tileable Laminate wood texture, photographed and made by me. CC0
Source Sojan Janso
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
Pattern produced in Paint.net using the Vibrato plug-in.
Source Firkin
From a drawing in 'Danmarks Riges Historie af J. Steenstrup, Kr. Erslev, A. Heise, V. Mollerup, J. A. Fridericia, E. Holm, A. D. Jørgensen', 1897.
Source Firkin
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.
Source Lazur URH
This is the remix of "plant pattern 02".I changed the object color to white and the BG to purple.The image a seamless pattern derived from a weed which I can't identify.The original weed image is from here:jp.pinterest.com/pin/500744052301423641/
Source Yamachem
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
A seamless background texture of old cardboard.
Source V. Hartikainen
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
I love cream! 50x50px and lovely in all the good ways.
Source Thomas Myrman
Prismatic Curved Diamond Pattern 4 No Background
Source GDJ
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin