Wasn't satisfied with the original's colouring. Too much component transfer and colormatrixes yet the results are lacking a bit. So this time it is a simple black to transparent fade, making it possible remixing easily once there will be other blending modes supported as well. Probably in inkscape 0.92.
Source Lazur URH
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
Submitted in a cream color, but you know how I like it.
Source Devin Holmes
A comeback for you: the popular Escheresque, now in black.
Source Patten
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Abstract Stars Geometric Pattern Prismatic 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
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
I have no idea how to describe this one, but it’s light and delicate.
Source JBasoo
Might not be super subtle, but quite original in its form.
Source Alex Smith
The edges of all the red objects line up either vertically or horizontally, but it doesn't appear so. Made from a square tile that can be got by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin
The Grid. A digital frontier. I tried to picture clusters of information as they traveled through the computer.
Source Haris Šumić
Non-seamless pattern drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
A free green background pattern with a pattern of rhombuses on a seamless texture. Feel free to use it as a tiled background image on your web site.
Source V. Hartikainen
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Psychedelic Geometric Background No Black
Source GDJ
CC0 and seamless wellington boot pattern.
Source SliverKnight
The image depicts a seamless pattern of Japanese Edo pattern called "kikkou-matsu" or "亀甲松" meaning " tortoiseshell-pinetree".The real pinetree is like this: https://jp.pinterest.com/pin/500744052301065077/
Source Yamachem
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
The image is a design of blue glass.How about using it as background image?
Source Yamachem