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
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
Prismatic Abstract Geometric Background 4
Source GDJ
Has nothing to do with toast, but it’s nice and subtle.
Source Pippin Lee
A bit of scratched up grayness. Always good.
Source Dmitry
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
Lovely pattern with some good-looking non-random noise lines.
Source Zucx
The image depicts a seamless pattern of Japanese Edo pattern called "kikkou-matsu" or "亀甲松" meaning " tortoiseshell-pinetree".The real pinetree is like this: https://jp.pinterest.com/pin/500744052301065077/
Source Yamachem
Prismatic Abstract Background Design No Black
Source GDJ
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
Prismatic Groovy Concentric Background No Black
Source GDJ
Seamless Light Background Texture.
Source V. Hartikainen
Inspired by a drawing in 'Poems', James Smith, 1881.
Source Firkin
Detailed but still subtle and quite original. Lovely gray shades.
Source Kim Ruddock
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
Prismatic Polka Dots Mark II 2 No Background
Source GDJ
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
Alternative colour scheme. 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
From a drawing in 'A Rolling Stone. A tale of wrongs and revenge', John Hartley, 1878.
Source Firkin
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio