Green Fibers #91
 Dark  CC BY-SA 3.0

The green fibers pattern will work very well in grayscale as well.

Source Matteo Di Capua

 More Textures
Background pattern pink and colours #2032
 Colorful  CC 0

A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.

Source Firkin

Tactile Noise@2X #6
 Dark  CC BY-SA 3.0

A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.

Source Atle Mo

Rocky Wall@2X #42
 Light  CC BY-SA 3.0

High detail stone wall with minor cracks and specks.

Source Projecteightyfive

Diamond pattern (colour 4) #2282
 Blue  CC 0

From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

“Transparent” Background Pattern@2X #494
 Light  CC 0

An emulated “transparent” background pattern, like that of all kinds of computer graphics software.

Source AdamStanislav

Cubes@2X #134
 Light  CC BY-SA 3.0

This reminds me of Game Cube. A nice light 3D cube pattern.

Source Sander Ottens

Background pattern 250 #2172
 Dark  CC 0

To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

Silver Scales@2X #190
 Light  CC BY-SA 3.0

Turn your site into a dragon with this great scale pattern.

Source Alex Parker

Star pattern #2410
 Brown  CC 0

A seamless pattern formed from a rectangular tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.

Source Firkin

Decorative divider 194 #2478
 Dark  CC 0

From a drawing in 'Friend or Fortune? The story of a strange year', Robert Overton, 1897.

Source Firkin

Nami@2X #576
 Dark  CC BY-SA 3.0

Not sure if this is related to the Nami you get in Google image search, but hey, it’s nice!

Source Dertig Media

Floral Pattern Background 5 #219
 Noise  CC 0

PDP

Source GDJ