This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
CC0 remixed from a drawing. Walter Crane, 1914, Firkin.
Source SliverKnight
The image depicts a tiled seamless pattern.The tile represents four leaves aligned every 90 ° , which may look like a bird or a dragon .The original leaf design is from a Japanese old book.
Source Yamachem
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
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 seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).
Source V. Hartikainen
A free seamless background image with abstract texture of green "curtain".
Source V. Hartikainen
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
Inspired by a 1930s wallpaper pattern I saw on TV.
Source Firkin
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Never out of fashion and so much hotter than the 45º everyone knows, here is a sweet 60º line pattern.
Source Atle Mo
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton
From a drawing in 'A Guide to the Guildhall of the City of London', John Baddeley, 1898.
Source Firkin
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
High detail stone wall with minor cracks and specks.
Source Projecteightyfive
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Remixed from a drawing in 'Analecta Eboracensia', Thomas Widdrington, 1897.
Source Firkin
From an image on opengameart.org shared by rubberduck.
Source Firkin