The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Background Wall, Art Abstract, Watercolor Vintage style CC0 texture.
Source Ractapopulous
Might not be super subtle, but quite original in its form.
Source Alex Smith
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
This is the remix of "blue wave-seigaiha".The image depicts a seamless pattern of the front upper part of Japanese five yen coin which is used currently.This design represents a rice with ripe golden ears.
Source Yamachem
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
A seamlessly tile-able grunge background image.
Source V. Hartikainen
Fake or not, it’s quite luxurious.
Source Factorio.us Collective
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
Sharp but soft triangles in light shades of gray.
Source Pixeden
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Same as Silver Scales, but in black. Turn your site into a dragon with this great scale pattern.
Source Alex Parker
Here's an yet another seamless note paper texture for use as a background on websites.
Source V. Hartikainen
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
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
A brown metallic grid pattern layered on top of a dark fabric texture. It should look great when using as a tiled background on web pages, especially blogs.
Source V. Hartikainen
Prismatic Abstract Geometric Background 5 No Black
Source GDJ