Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
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
You know I’m a sucker for these. Well-crafted paper pattern.
Source Mihaela Hinayon
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
The tile can be had by using shift+alt+i on the selected rectangle in Inkscape
Source Firkin
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A free pink background pattern.
Source V. Hartikainen
CC0 and seamless wellington boot pattern.
Source SliverKnight
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
Inspired by a drawing seen in 'City of Liverpool', James Picton, 1883.
Source Firkin
Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.
Source Firkin
A floral background formed from numerous clones of flower 117.
Source Firkin
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem