Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
Prismatic Basic Pattern 2 No Background
Source GDJ
Abstract Tiled Background Extended 11
Source GDJ
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
It’s like Shine Dotted’s sister, only rotated 45 degrees.
Source mediumidee
Coming in at 666x666px, this is an evil big pattern, but nice and soft at the same time.
Source Atle Mo
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
This was formed by distorting an image of a background on Pixabay.
Source Firkin
The following orange background pattern resembles a honeycomb.
Source V. Hartikainen
Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
A free seamless background image with a texture of dark red "canvas". It should look very nice on web sites.
Source V. Hartikainen
Prismatic Hexagonalism Pattern No Background
Source GDJ
Prismatic Abstract Geometric Background 4
Source GDJ
Remixed from a drawing in 'Очерки Русской Исторіи въ памятникахъ быта', Petr Polevoi, 1879.
Source Firkin
More Japanese-inspired patterns, Gold Scales this time.
Source Josh Green
A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).
Source V. Hartikainen
Paper model of a tetrahedron. Modelo de papel de um tetraedro.
Source laobc
Remixed from an image on Pixabay uploaded by Prawny
Source Firkin
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
A free seamless background texture that looks like a brown stone wall.
Source V. Hartikainen
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
From a drawing in 'Kingsdene', Maria Fetherstonehaugh, 1878.
Source Firkin
Remixed from a drawing in 'Kulturgeschichte der Deutschen im Mittelalter' Franz von Loeher, 1891. The unit tile can be had by selecting the rectangle in Inkscape and using shift-alt-i
Source Firkin