From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
Retro Circles Background 7 No Black
Source GDJ
Prismatic Groovy Concentric Background 2
Source GDJ
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
I’m starting to think I have a concrete wall fetish.
Source Atle Mo
A free pink background pattern.
Source V. Hartikainen
A blue background wallpaper for websites. It has a seamless texture with vertical stripes. It looks quite nice not only when using as a tiled background on websites, but also on computer desktops.
Source V. Hartikainen
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
A seamless background pattern with impressed gray dots.
Source V. Hartikainen
Prismatic Triangular Seamless Pattern III With Background
Source GDJ
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
Not the Rebel alliance, but a dark textured pattern.
Source Hendrik Lammers
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Super detailed 16×16 tile that forms a beautiful pattern of straws.
Source Pavel
A seamless texture of worn out "cardboard".
Source V. Hartikainen