3px Tile #342
 Dark  CC BY-SA 3.0

Tiny dark square tiles with varied color tones.

Source Gre3g

 More Textures
Darth Stripe #99
 Dark  CC BY-SA 3.0

Diagonal lines with a lot of texture to them.

Source Ashton

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

Abstract Stars Geometric Pattern Prismatic No Background #384
 Noise  CC 0

Abstract Stars Geometric Pattern Prismatic No Background

Source GDJ

Black Linen@2X #64
 Dark  CC BY-SA 3.0

In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.

Source Atle Mo

Bright Multicolored Floral Background #559
 Noise  CC 0

Bright Multicolored Floral Background by Karen Arnold from PDP.

Source GDJ

Visual illusion #2586
 Grid  CC 0

The edges of all the red objects line up either vertically or horizontally, but it doesn't appear so. Made from a square tile that can be got by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin