Remixed from a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A free seamless background image with abstract texture of green "curtain".
Source V. Hartikainen
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Subtle scratches on a light gray background.
Source Andrey Ovcharov
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
ZeroCC tileable mossy (lichen) stone texture, edited from pixabay. CC0
Source Sojan Janso
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
The classic notebook paper with horizontal stripes.
Source Are Sundnes
I have no idea how to describe this one, but it’s light and delicate.
Source JBasoo
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
Prismatic Snowflakes Pattern 3 No Background
Source GDJ
This makes me wanna shoot some pool! Sweet green pool table pattern.
Source Caveman
An alternative colour scheme to the original seamless pattern.
Source Firkin
If you don’t like cream and pixels, you’re in the wrong place.
Source Mizanur Rahman
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
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
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman