Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Prismatic Abstract Line Art Pattern Background
Source GDJ
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
A dark metallic background with a pattern of stamped dots. Here's a dark "metallic" background pattern for you.
Source V. Hartikainen
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Remixed from an image on Pixabay, the original having been uploaded by darkmoon1968.
Source Firkin
A new one called white wall, not by me this time.
Source Yuji Honzawa
I skipped number 3, because it wasn’t all that great. Sorry.
Source Dima Shiper
More leather, and this time it’s bigger! You know, in case you need that.
Source Elemis
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
Background pattern made in "Grunge-Like" style. Available in both SVG and JPG formats. Edit to your needs then click the download button.
Source V. Hartikainen
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
Prismatic Groovy Concentric Background 4
Source GDJ
Remixed from a PNG that was uploaded to Pixabay by VictorianLady
Source Firkin
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
Colorful Floral Background 3 No Black
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
Prismatic Hypnotic Pattern 2 No Background
Source GDJ
A seamless pattern formed from a modified version of rwwgub's tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
There are many carbon patterns, but this one is tiny.
Source Designova
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
A bit of scratched up grayness. Always good.
Source Dmitry