A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
A large pattern with funky shapes and form. An original. Sort of origami-ish.
Source Luuk van Baars
Prismatic Curved Diamond Pattern No Background
Source GDJ
Seamless tile drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Heavily remixed from a drawing in 'Barbara Leybourne; a story of eighty years ago', Sarah Hamer, 1889.
Source Firkin
Remixed from a raster on Pixabay that was uploaded by ArtsyBee.
Source Firkin
This seamless pattern consists of a blue grid on a yellow background.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
Feel free to download this "Dark Wood" background texture for your web site. The background tiles seamlessly!
Source V. Hartikainen
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Prismatic Triangular Seamless Pattern III With Background
Source GDJ
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer