Like the name suggests, this background image consists of a pattern of dark bricks. It may be an option for you, if you are looking for something that looks like a brick wall for use as a background on web pages. It's not a masterpiece, but looks pretty nice when is tiled.
Source V. Hartikainen
Stefan is hard at work, this time with a funky pattern of squares.
Source Stefan Aleksić
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Retro Circles Background 7 No Black
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Remixed from a JPG that was uploaded to Pixabay by Osckar
Source Firkin
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
From a drawing of the coat of arms of the Ottoman Empire on Wikimedia.
Source Firkin
Number five from the same submitter, makes my job easy.
Source Dima Shiper
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
This seamless pattern consists of a blue grid on a yellow background.
Source V. Hartikainen
The starting point for this was a texture drawn with the 'Radial Colors' plug-in in Paint.net.
Source Firkin
Remixed from a drawing in 'Some account of the Worshipful Company of Ironmongers', John Nicholl, 1866.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo
A seamless pattern formed from a tile made from page ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin