Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
A seamless background pattern with impressed gray dots.
Source V. Hartikainen
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
This is the remix of "polka dot seamless pattern".The image depicts polka dot seamless pattern.
Source Yamachem
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
8 by 8 pixels, and just what the title says.
Source pixilated
Prismatic Groovy Concentric Background 2
Source GDJ
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
From a drawing in 'From Snowdon to the Sea. Striking stories of North and South Wales', Marie Trevelyan, 1895.
Source Firkin
Remixed from a drawing that was uploaded to Pixabay by captenpub.
Source Firkin
A light background pattern with diagonal stripes. Here's a simple light striped background for you.
Source V. Hartikainen
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
Prismatic Abstract Line Art Pattern Background
Source GDJ