Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
A heavy hitter at 400x400px, but lovely still.
Source Breezi
From a drawing in 'A Life Interest', Mrs Alexander, 1888.
Source Firkin
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
This is the remix of an OCAL clipart called "Art Nouveau ornament" uploaded by "microcosme".Thanks.This is a seamless pattern of an Art Nouveau ornament.
Source Yamachem
Bright Multicolored Floral Background by Karen Arnold from PDP.
Source GDJ
Wild Oliva or Oliva Wilde? Darker than the others, sort of a medium dark pattern.
Source Badhon Ebrahim
A pale yellow background pattern with vertical stripes. The stripes are partially faded. I think this background image turned out pretty well, especially those faded stripes.
Source V. Hartikainen
Derived from a drawing in 'Historiske Afhandlinger', Adolf Jorgensen, 1898.
Source Firkin
A version without colours blended together to give a different look.
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
A light background pattern with diagonal stripes. Here's a simple light striped background for you.
Source V. Hartikainen
A chequerboard pattern with a fruit theme. The fruits are from a posting by inkscapeforum.it.
Source Firkin
White handmade paper pattern with small bumps.
Source Marquis
Bright Multicolored Floral Background by Karen Arnold from PDP.
Source GDJ
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin