This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
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
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
The tile for this is based on a repeating unit close to a design on Pixabay. It can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A repeating background of thick textured paper. Actually, it turned out to look like something between a paper and fabric.
Source V. Hartikainen
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper