The image depicts a Japanese Edo pattern called "kanoko or 鹿の子" meaning "fawn" which has a fur with small white spots.
Source Yamachem
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
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
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
The classic notebook paper with horizontal stripes.
Source Are Sundnes
I have no idea what J Boo means by this name, but hey – it’s hot.
Source j Boo
Prismatic Groovy Concentric Background
Source GDJ
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges
More Japanese-inspired patterns, Gold Scales this time.
Source Josh Green
Remixed from a raster on Pixabay, that was uploaded by ArtsyBee.
Source Firkin
This is a seamless pattern which is derived from a flower petal image.
Source Yamachem
Number five from the same submitter, makes my job easy.
Source Dima Shiper
A bit of scratched up grayness. Always good.
Source Dmitry
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
It’s an egg, in the form of a pattern. This really is 2012.
Source Paul Phönixweiß
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin