I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
It’s an egg, in the form of a pattern. This really is 2012.
Source Paul Phönixweiß
A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A seamless pattern based on a tile that can be achieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
This one needs to be used in small areas; you can see it repeat.
Source Luca
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
Prismatic Curved Diamond Pattern 2 No Background
Source GDJ
Pattern produced in Paint.net using the Vibrato plug-in.
Source Firkin
Lovely light gray floral motif with some subtle shades.
Source GraphicsWall
This light yellow background pattern consists of an irregular pattern of spots. Here's a light background pattern with yellowish tint.
Source V. Hartikainen
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Remixed from a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Remixed from a drawing in 'Jezebel's Daughter', Wilkie Collins 1880
Source Firkin
Everyone needs some stardust. Sprinkle it on your next project.
Source Atle Mo
Zero CC tileable cork floor, photographed and made by me. CC0
Source Sojan Janso
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
Fabric-ish patterns are close to my heart. French Stucco to the rescue.
Source Christopher Buecheler
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin