From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
A nice and simple gray stucco material. Great on its own, or as a base for a new pattern.
Source Bartosz Kaszubowski
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Zero CC tileable wood texture, made by me procedurally in Neo Texture Edit.
Source Sojan Janso
Pattern Background, Texture, Photoshop Structure style CC0 texture.
Source Darkmoon1968
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
This is the third pattern called Dark Denim, but hey, we all love them!
Source Brandon Jacoby
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
On a large canvas you can see it tiling, but used on smaller areas, it’s beautiful.
Source Paul Phönixweiß
Formed from decorative divider 184 in paint.net. Vectorised with Vector Magic.
Source Firkin
Hey, you never know when you’ll need a bird pattern, right?
Source Pete Fecteau
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry