Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
A dark pattern made out of 3×3 circles and a 1px shadow. This works well as a carbon texture or background.
Source Atle Mo
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
Abstract Tiled Background Extended 10
Source GDJ
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
Prismatic Hexagonalism Pattern No Background
Source GDJ
Background pattern made in "Grunge-Like" style. Available in both SVG and JPG formats. Edit to your needs then click the download button.
Source V. Hartikainen
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Fake or not, it’s quite luxurious.
Source Factorio.us Collective
The image is a design of blue glass.How about using it as background image?
Source Yamachem
A free seamless background image with a texture of dark red "canvas". It should look very nice on web sites.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 4 No Background
Source GDJ
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin