I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
A pale orange background pattern with glossy groove stripes.
Source V. Hartikainen
This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
White handmade paper pattern with small bumps.
Source Marquis
Remixed from a drawing in 'Canadian forest industries July-December', 1915
Source Firkin
Nice little grid. Would work great as a base on top of some other patterns.
Source Arno Gregorian
This is the remix of "Colorful Floral Pattern Background 3" uploaded by "GDJ". Thanks.
Source Yamachem
This metal background pattern resembles a metal plate with rivets. Solid rivets on a metal plate.
Source V. Hartikainen
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
One more brick pattern. A bit more depth to this one.
Source Benjamin Ward
If you’re sick of the fancy 3D, grunge and noisy patterns, take a look at this flat 2D brick wall.
Source Listvetra
More in the paper realm, this time with fibers.
Source Jorge Fuentes
Zero CC tileable ground (#2) cracked, crackled texture, made by me. CC0
Source Sojan Janso
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
If you don’t like cream and pixels, you’re in the wrong place.
Source Mizanur Rahman
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
Here's a quite bright pink background pattern for use on websites. It doesn't look like a real fur, but it definitely resembles one.
Source V. Hartikainen
Background pattern originally a PNG drawn in Paint.net
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer