Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
A background tile for web with abstract repeating texture of dark "stone wall".
Source V. Hartikainen
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
From a drawing in 'Hundert Jahre in Wort und Bild', S. Stefan, 1899.
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
On a large canvas you can see it tiling, but used on smaller areas, it’s beautiful.
Source Paul Phönixweiß
Prismatic Groovy Concentric Background 2
Source GDJ
Nothing like a clean set of bed sheets, huh?
Source Badhon Ebrahim
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Prismatic Triangular Background Design Mark II 5
Source GDJ
Found on the ground in french cafe in kunming, Yunnan, china
Source Rejon
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ