Subtle scratches on a light gray background.
Source Andrey Ovcharov
Prismatic Hypnotic Pattern No Background
Source GDJ
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
From a drawing in 'Hundert Jahre in Wort und Bild', S. Stefan, 1899.
Source Firkin
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
The image depicts polka dot seamless pattern.
Source Yamachem
Seamless pattern formed from a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
Retro Circles Background 4 No Black
Source GDJ
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
Lovely pattern with some good-looking non-random noise lines.
Source Zucx
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
I’m guessing this is related to the Sony Vaio? It’s a nice pattern no matter where it’s from.
Source Zigzain
You know you can’t get enough of these linen-fabric-y patterns.
Source James Basoo
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
Abstract Ellipses Background Grayscale
Source GDJ
From an image on opengameart.org shared by rubberduck.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Based on an image that was uploaded to Pixabay by devanath
Source Firkin