Pattern Background, Texture, Photoshop Structure style CC0 texture.
Source Darkmoon1968
Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
Prismatic Polka Dots Mark II No Background
Source GDJ
Fake or not, it’s quite luxurious.
Source Factorio.us Collective
A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
This background image has seamless texture that resembles a surface of gray stone.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
I’m guessing this is related to the Sony Vaio? It’s a nice pattern no matter where it’s from.
Source Zigzain
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A floral background formed from numerous clones of flower 117.
Source Firkin
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein