You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova
Prismatic Groovy Concentric Background 2
Source GDJ
From a drawing in 'Real Sailor-Songs', John Ashton, 1891.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay, CC0
Source Sojan Janso
Prismatic Snowflakes Pattern No Background
Source GDJ
A repeatable image with dark background and metal grid pattern.
Source V. Hartikainen
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
Remixed from a JPG that was uploaded to Pixabay by theasad121
Source Firkin
The original enhanced with some gradients.
Source Firkin
Prismatic Rounded Squares Grid 3 No Background
Source GDJ
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
Here's a bluish gray striped background pattern for use on web sites.
Source V. Hartikainen
From a drawing in 'A Guide to the Guildhall of the City of London', John Baddeley, 1898.
Source Firkin
A seamless web texture of "green stone".
Source V. Hartikainen
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
By popular request, an outline version of the pentagon pattern.
Source Atle Mo
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
A pale orange background pattern with glossy groove stripes.
Source V. Hartikainen
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin