Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Floral patterns will never go out of style, so enjoy this one.
Source Lasma
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
This is a seamless pattern of regular hexagon which has a honeycomb structure.
Source Yamachem
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Prismatic Abstract Geometric Background 4
Source GDJ
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Remixed from a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Abstract Line Art Pattern Background
Source GDJ
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
An orange vertically striped background pattern. Feel free to download and use this orange background pattern, for example, on the web). It resembles a wallpaper with vertical stripes or something similar to it.
Source V. Hartikainen
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
Seamless SVG vector and JPG backgrounds with faded diagonal stripes. The colors are editable.
Source V. Hartikainen
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
A re-make of the Gradient Squares pattern.
Source Dimitar Karaytchev