I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
From a drawing in 'Real Sailor-Songs', John Ashton, 1891.
Source Firkin
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.
Source Firkin
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
emixed from a JPG that was uploaded to Pixabay by Kyotime
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
Psychedelic Geometric Background No Black
Source GDJ
A free black metallic background pattern. Here's a new pattern I made that looks metallic.
Source V. Hartikainen
It’s like Shine Dotted’s sister, only rotated 45 degrees.
Source mediumidee
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Seamless Green Tile Background
Source V. Hartikainen
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Prismatic Abstract Geometric Background 4
Source GDJ
The classic notebook paper with horizontal stripes.
Source Are Sundnes
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow