Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
This is the remix of "polka dot seamless pattern".The image depicts polka dot seamless pattern.
Source Yamachem
Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
A version without colours blended together to give a different look.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
Prismatic Polyskelion Pattern No Background
Source GDJ
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
This one is quite simple in design, it consists of vertical stripes layered on top of a seamless texture.
Source V. Hartikainen
Number five from the same submitter, makes my job easy.
Source Dima Shiper
Bumps, highlight and shadows – all good things.
Source Badhon Ebrahim
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A fun-looking elastoplast/band-aid pattern. A hint of orange tone in this one.
Source Josh Green
Background Wall, Art Abstract, Star Well & CC0 texture.
Source Ractapopulous
Prismatic Abstract Geometric Background derived from an image on Pixabay.
Source GDJ
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight