The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
Prismatic Groovy Concentric Background
Source GDJ
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
Sort of reminds me of those old house wallpapers.
Source Tish
Abstract Tiled Background Extended 11
Source GDJ
Inspired by a drawing in 'Poems', James Smith, 1881.
Source Firkin
A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
From a drawing in 'La Principauté de Liège et les Pays-Bas au XVIe siècle', Société des Bibliophiles Liégeois ,1887.
Source Firkin
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Zero CC tileable ground cracked, crackled, texture, made by me.
Source Sojan Janso
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
The basic shapes never get old. Simple triangle pattern.
Source Atle Mo
You know, tiny and sharp. I’m sure you’ll find a use for it.
Source Atle Mo
A tile-able background for websites with paper-like texture and a grid pattern layered on top of it.
Source V. Hartikainen
An abstract texture of black metal pipes (seamless).
Source V. Hartikainen
A bit simplified version. Although it could be edited out to be simpler. Anyway, this time the tiling is converted to a pattern fill -which is using clipping for the tile's edges.
Source Lazur URH
Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.
Source Firkin