This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Little x’es, noise and all the stuff you like. Dark like a Monday, with a hint of blue.
Source Tom McArdle
This beige background pattern resembles a concrete wall with engravings or something similar to it.
Source V. Hartikainen
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
The texture of this background image has some similarities with leather, and it's colored in a dark brown color. So, if you are looking for a dark brown background image for your website, this may be an option for you.
Source V. Hartikainen
Zero CC tileable Laminate wood texture, photographed and made by me. CC0
Source Sojan Janso
A comeback for you: the popular Escheresque, now in black.
Source Patten
From a drawing in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
A repeating background with seamless texture of stone. There haven't been any stone-like backgrounds for a while, so I have decided to create one more. The rest can be found in the appropriate category.
Source V. Hartikainen
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
The perfect pattern for all your blogs about type, or type-related matters.
Source Atle Mo
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
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
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
From an image on opengameart.org shared by rubberduck.
Source Firkin
This background pattern contains a texture of yellow wood planks. I think it looks quite original.
Source V. Hartikainen
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin