This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
A comeback for you: the popular Escheresque, now in black.
Source Patten
Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
Remixed from a drawing that was uploaded to Pixabay by captenpub.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
A background tile of dark textile. Made this a long time ago and just now decided to publish it.
Source V. Hartikainen
This seamless pattern consists of a blue grid on a yellow background.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
As the original image 's page size is too large for its image size, I remixed it.
Source Yamachem
Used the 6th circle pattern designed by Viscious-Speed to create a print that can be used for card making or scrapbooking. Save as a PDF file for the best printing option.
Source Lovinglf
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 3
Source GDJ
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
Prismatic Groovy Concentric Background No Black
Source GDJ