Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Black & white version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Wild Oliva or Oliva Wilde? Darker than the others, sort of a medium dark pattern.
Source Badhon Ebrahim
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
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
Feel free to download this "Dark Wood" background texture for your web site. The background tiles seamlessly!
Source V. Hartikainen
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
It’s an egg, in the form of a pattern. This really is 2012.
Source Paul Phönixweiß
Lovely pattern with splattered vintage speckles.
Source David Pomfret
Abstract Ellipses Background Grayscale
Source GDJ
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
I’m starting to think I have a concrete wall fetish.
Source Atle Mo
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Seamless Light Background Texture.
Source V. Hartikainen
No idea what Nistri means, but it’s a crisp little pattern nonetheless.
Source Markus Reiter
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Prismatic Polka Dots 3 No Background
Source GDJ
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin