People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
A seamless texture of black leather. I think it will look best when used in headers, footers or sidebars.
Source V. Hartikainen
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
Zero CC tileable Laminate wood texture, photographed and made by me. CC0
Source Sojan Janso
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
The image depicts a seamless pattern of pine tree leaves.
Source Yamachem