This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
One can never have too few rice paper patterns, so here is one more.
Source Atle Mo
Fabric-ish patterns are close to my heart. French Stucco to the rescue.
Source Christopher Buecheler
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova
A bit strange this one, but nice at the same time.
Source Diogo Silva
A bit like some carbon, or knitted netting if you will.
Source Anna Litvinuk
Prismatic Chevrons Pattern 5 With Background
Source GDJ
A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Little x’es, noise and all the stuff you like. Dark like a Monday, with a hint of blue.
Source Tom McArdle
Adapted from an image that was uploaded to Pixabay by Anerma.
Source Firkin
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
Free tiled background with colorful stripes and white splatter.
Source V. Hartikainen