Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
From a drawing in 'Bond Slaves. The story of a struggle.', Isabella Varley, 1893.
Source Firkin
8 by 8 pixels, and just what the title says.
Source pixilated
A free background pattern with abstract green tiles.
Source V. Hartikainen
Light gray pattern with an almost wall tile-like appearance.
Source Markus Tinner
An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
Colour version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Zero CC tileable wood texture, made by me procedurally in Neo Texture Edit.
Source Sojan Janso
Oh yes, it happened! A pattern in full color.
Source Atle Mo
Love the style on this one, very fresh. Diagonal diamond pattern. Get it?
Source INS
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
By popular request, an outline version of the pentagon pattern.
Source Atle Mo
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
A seamless pattern of "sewn stripes" colored in light gray.
Source V. Hartikainen
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Alternative colour scheme for the original floral pattern.
Source Firkin
Clean and crisp lines all over the place. Wrap it up with this one.
Source Dax Kieran
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
This is a hot one. Small, sharp and unique.
Source GraphicsWall
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo