The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
Inspired by a drawing seen in 'City of Liverpool', James Picton, 1883.
Source Firkin
A light gray fabric pattern with faded vertical stripes.
Source V. Hartikainen
Tile available in Inkscape using shift-alt-i on the selected rectangle
Source Firkin
Zero CC tileable dry grass texture, photographed and made by me. CC0
Source Sojan Janso
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
There are many carbon patterns, but this one is tiny.
Source Designova
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
If you need a green background for your blog/website, try this one. Remember that Green Striped Background is seamlessly tileable.
Source V. Hartikainen
The image is a seamless pattern of a fishnet.
Source Yamachem
A black tile-able background with paper-like texture.
Source V. Hartikainen
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Remixed from a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Prismatic Groovy Concentric Background 3 No Black
Source GDJ