The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker
This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
A seamless pattern formed from cross 4. To get the original tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
You know you love wood patterns, so here’s one more.
Source Richard Tabor
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
A bit like some carbon, or knitted netting if you will.
Source Anna Litvinuk