This was formed by distorting an image of a background on Pixabay.
Source Firkin
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Scanned some rice paper and tiled it up for you. Enjoy.
Source Atle Mo
Tile available in Inkscape using shift-alt-i on the selected rectangle
Source Firkin
Seamless pattern the basic tile for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
An attempt for cleaning up the original image in a few steps.
Source Lazur URH
An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
Imagine you zoomed in 1000X on some fabric. But then it turned out to be a skeleton!
Source Angelica
Abstract Stars Geometric Pattern Prismatic No Background
Source GDJ
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
A dark gray, sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
Everyone needs some stardust. Sprinkle it on your next project.
Source Atle Mo
Black And White Floral Pattern Background Inverse
Source GDJ
An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
This tiled background comes in red and consists of tiles that look like gemstones. It is more for blogs or social profiles, I think.
Source V. Hartikainen