Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
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
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
Never out of fashion and so much hotter than the 45º everyone knows, here is a sweet 60º line pattern.
Source Atle Mo
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Could be paper, could be a Polaroid frame – up to you!
Source Chaos
A textured orange background pattern with vertical stripes.
Source V. Hartikainen
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
No, not the band but the pattern. Simple squares in gray tones, of course.
Source Atle Mo
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
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
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Prismatic Geometric Pattern Background No Black
Source GDJ
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
Have you wondered about how it feels to be buried alive? Here is the pattern for it.
Source Hendrik Lammers
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
A repeating background of thick textured paper. Actually, it turned out to look like something between a paper and fabric.
Source V. Hartikainen
A bit strange this one, but nice at the same time.
Source Diogo Silva
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A free pink background pattern.
Source V. Hartikainen
Prismatic Curved Diamond Pattern No Background
Source GDJ
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin