A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Same classic 45-degree pattern, dark version.
Source Luke McDonald
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
This background has abstract texture with some similarities to wood.
Source V. Hartikainen
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
Prismatic Geometric Pattern Background
Source GDJ
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Prismatic Hexagonalism Pattern No Background
Source GDJ
A background pattern with wavy green vertical stripes. This one has green stripes on a white background. Download if you like it.
Source V. Hartikainen
I guess this is inspired by the city of Ravenna in Italy and its stone walls.
Source Sentel
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Not sure if this is related to the Nami you get in Google image search, but hey, it’s nice!
Source Dertig Media
From an image on opengameart.org shared by rubberduck.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
The image depicts a Japanese Edo pattern called "kanoko or 鹿の子" meaning "fawn" which has a fur with small white spots.
Source Yamachem
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
Inspired by a 1930s wallpaper pattern I saw on TV.
Source Firkin
A seamlessly tile-able grunge background image.
Source V. Hartikainen
Abstract Tiled Background Extended 12
Source GDJ