Carbon Fiber #3
 Carbon  CC BY-SA 3.0

A dark pattern made out of 3×3 circles and a 1px shadow. This works well as a carbon texture or background.

Source Atle Mo

 More Textures
Diamond pattern 2 (colour 4) #2265
 Red  CC 0

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

Source Firkin

Black Linen #63
 Dark  CC BY-SA 3.0

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

Source Atle Mo

Prismatic Curved Diamond Pattern 3 No Background@2X #540
 Diamond  CC 0

Prismatic Curved Diamond Pattern 3 No Background

Source GDJ

Colourful background #2009
 Colorful  CC 0

Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic

Source Firkin

Prismatic Groovy Concentric Background No Black #451
 Noise  CC 0

Prismatic Groovy Concentric Background No Black

Source GDJ

Starting Diamond Shape@2X #138
 Light  CC 0

Simple blue and line to mix.

Source SliverKnight

Prismatic Geometric Tessellation Pattern No Background@2X #552
 Noise  CC 0

Prismatic Geometric Tessellation Pattern No Background

Source GDJ

Prismatic Abstract Line Art Pattern Background@2X #566
 Dark  CC 0

Prismatic Abstract Line Art Pattern Background

Source GDJ