This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
A dark metallic background with a pattern of stamped dots. Here's a dark "metallic" background pattern for you.
Source V. Hartikainen
Prismatic Abstract Geometric Background 4
Source GDJ
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
Submitted as a black pattern, I made it light and a few steps more subtle.
Source Andy
A dark gray, sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Could be paper, could be a Polaroid frame – up to you!
Source Chaos
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
The image depicts an edo-era pattern called "same-komon" or "鮫小紋"which looks like a shark skin.The "same" in Japanese means shark in English.
Source Yamachem
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
The image is a remix of "edo pattern-samekomon".I changed the color of dots from black to white and added BG in light-brown.
Source Yamachem