There are many carbon patterns, but this one is tiny.
Source Designova
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
You know you can’t get enough of these linen-fabric-y patterns.
Source James Basoo
Used the 6th circle pattern designed by Viscious-Speed to create a print that can be used for card making or scrapbooking. Save as a PDF file for the best printing option.
Source Lovinglf
Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova
Prismatic Groovy Concentric Background
Source GDJ
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
This is lovely, just the right amount of subtle noise, lines and textures.
Source Richard Tabor
A pattern derived from part of a fractal rendering in Paint.net.
Source Firkin
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
I guess this is inspired by the city of Ravenna in Italy and its stone walls.
Source Sentel
Seamless Green Tile Background
Source V. Hartikainen
This background has abstract texture with some similarities to wood.
Source V. Hartikainen
This white background pattern has a seamless grunge style texture. Here's a white grunge style background pattern. Use it as a tiled background image on web sites or for other purposes.
Source V. Hartikainen
A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.
Source Dima Shiper
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
A seamless web texture with illustration of pale color stains on canvas.
Source V. Hartikainen
Not even 1kb, but very stylish. Gray thin lines.
Source Struck Axiom
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin