From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
CC0 and seamless wellington boot pattern.
Source SliverKnight
Tile available in Inkscape using shift-alt-i on the selected rectangle
Source Firkin
From a drawing in 'Hundert Jahre in Wort und Bild', S. Stefan, 1899.
Source Firkin
Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
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
Remixed from a drawing in 'Prehistoric Man: researches into the origin of civilisation in the old and the new world', Daniel Wilson, 1876.
Source Firkin
Derived from an image that was uploaded to Pixabay by mdmelo.
Source Firkin
Formed from decorative divider 184 in paint.net. Vectorised with Vector Magic.
Source Firkin
First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.
Source Atle Mo
From a drawing in 'Hyde Park from Domesday-Book to date', John Ashton, 1896.
Source Firkin
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova
Remixed from a drawing in 'A Girl in Ten Thousand', Elizabeth Meade, 1896.
Source Firkin
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
The image depicts a seamless pattern made using a bird's face.
Source Yamachem
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Prismatic Geometric Tessellation Pattern 3 No Background
Source GDJ
Fix and cc0 to get the tile this is based on.
Source SliverKnight
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
A free seamless background texture that looks like a brown stone wall.
Source V. Hartikainen
Just like your old suit, all striped and smooth.
Source Alex Berkowitz
A bit like some carbon, or knitted netting if you will.
Source Anna Litvinuk