Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.
Source Dima Shiper
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
From a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
Prismatic Abstract Background Design No Black
Source GDJ
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
The following orange background pattern resembles a honeycomb.
Source V. Hartikainen
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
A green background pattern with warped vertical stripes and a grunge look.
Source V. Hartikainen
Colorful Floral Background 3 No Black
Source GDJ
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a drawing in 'Jardyne's Wife', Charles Wills, 1891.
Source Firkin
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
Tiny circle waves, almost like the ocean.
Source Sagive
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion
A large pattern with funky shapes and form. An original. Sort of origami-ish.
Source Luuk van Baars
Prismatic Polka Dots 3 No Background
Source GDJ
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin