This is so subtle you need to bring your magnifier!
Source Carlos Valdez
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
Looks like an old rug or a computer chip.
Source Patutin Sergey
A free seamless background pattern for use on websites.
Source V. Hartikainen
From drawing in 'Musings in Maoriland', Thomas Bracken, 1890.
Source Firkin
A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
A comeback for you: the popular Escheresque, now in black.
Source Patten
Colorful Floral Background No Black
Source GDJ
A seamless texture of black leather. I think it will look best when used in headers, footers or sidebars.
Source V. Hartikainen
Retro Circles Background 4 No Black
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
It’s big, it’s gradient—and it’s square.
Source Brankic1979
This one is amazing, truly original. Go use it!
Source Viahorizon
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin