A comeback for you: the popular Escheresque, now in black.
Source Patten
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Derived from a drawing in 'Elfrica. An historical romance of the twelfth century', Charlotte Boger, 1885
Source Firkin
A light gray background pattern with seamless fabric-like texture and almost unnoticeable stripes.
Source V. Hartikainen
You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
Green Background Pattern
Source V. Hartikainen
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
ZeroCC tileable mossy (lichen) stone texture, edited from pixabay. CC0
Source Sojan Janso
It looks very nice I think.
Source V. Hartikainen
This makes me wanna shoot some pool! Sweet green pool table pattern.
Source Caveman
More in the paper realm, this time with fibers.
Source Jorge Fuentes
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
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
Remixed from a JPG that was uploaded to Pixabay by susanlu4esm
Source Firkin
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
Zero CC tileable hard cover green book, scanned and made by me. CC0
Source Sojan Janso
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
A heavy hitter at 400x400px, but lovely still.
Source Breezi
This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers