From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.
Source Atle Mo
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Prismatic Geometric Pattern Background
Source GDJ
Seamless Olive Green Web Background Image
Source V. Hartikainen
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
Seamless Green Tile Background
Source V. Hartikainen
Wild Oliva or Oliva Wilde? Darker than the others, sort of a medium dark pattern.
Source Badhon Ebrahim
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
Kaleidoscope Prismatic Abstract No Background
Source GDJ
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Black & white version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
This is the remix of an OCAL clipart called "Rain on Window" uploaded by "pagarmidna".Thanks.This is a seamless pattern of raindrops.
Source Yamachem
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Orange-red pattern for tiled backgrounds.
Source V. Hartikainen
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Colorful Floral Background No Black
Source GDJ
Looks like an old rug or a computer chip.
Source Patutin Sergey