A nice one indeed, but I have a feeling we have it already? If you spot a copy, let me know on Twitter.
Source Graphiste
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
Seamless Prismatic Quadrilateral Line Art Pattern No Background
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Almost like little fish shells, or dragon skin.
Source Graphiste
Geometric triangles seem to be quite hot these days.
Source Pixeden
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
Gold Triangular Seamless Pattern No Background
Source GDJ
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
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
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A free black metallic background pattern. Here's a new pattern I made that looks metallic.
Source V. Hartikainen
A free seamless background image with abstract texture of green "curtain".
Source V. Hartikainen
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
Submitted as a black pattern, I made it light and a few steps more subtle.
Source Andy