From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
Awesome name, great pattern. Who does not love space?
Source Nick Batchelor
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
A free seamless background image with a texture of dark red "canvas". It should look very nice on web sites.
Source V. Hartikainen
Zero CC tileable yellow craft paper; scanned and made by me. CC0
Source Sojan Janso
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
Background Wall, Art Abstract, Watercolor Vintage style CC0 texture.
Source Ractapopulous
A seamless texture of worn out "cardboard".
Source V. Hartikainen
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
Seamless Green Tile Background
Source V. Hartikainen
From a drawing in 'Cassell's Library of English Literature', Henry Morley, 1883.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
Seamless tile drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
This tiled background comes in red and consists of tiles that look like gemstones. It is more for blogs or social profiles, I think.
Source V. Hartikainen
A very dark asfalt pattern based off of a photo taken with my iPhone.
Source Atle Mo
Black And White Floral Pattern Background from PDP.
Source GDJ
A version without colours blended together to give a different look.
Source Firkin
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
Prismatic Groovy Concentric Background 4
Source GDJ