Sometimes you just need the simplest thing.
Source Fabricio
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Brushed aluminum, in a bright gray version. Lovely 2X as well.
Source Andre Schouten
This was formed by distorting an image of a background on Pixabay.
Source Firkin
It’s an egg, in the form of a pattern. This really is 2012.
Source Paul Phönixweiß
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
White circles connecting on a light gray background.
Source Mark Collins
Light gray paper pattern with small traces of fiber and some dust.
Source Atle Mo
Clean and crisp lines all over the place. Wrap it up with this one.
Source Dax Kieran
Detailed but still subtle and quite original. Lovely gray shades.
Source Kim Ruddock
A beautiful dark padded pattern, like an old classic sofa.
Source Chris Baldie
Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.
Source Firkin
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
The image depicts a seamless pattern of a Japanese family crest called "chidori" in Japanese .A chidori in Japanese means a plover in English.
Source Yamachem
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning