Double Lined #51
 Stripes  CC BY-SA 3.0

Horizontal and vertical lines on a light gray background.

Source Adam Anlauf

 More Textures
Background pattern 1 #220
 Noise  CC 0

A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.

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

Background pattern 226 (colour 5) #2317
 Blue  CC 0

A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.

Source Firkin

Retro Circles Background 4@2X #421
 Dark  CC 0

Retro Circles Background 4

Source GDJ

Prismatic Hexagonalism Pattern No Background #391
 Light  CC 0

Prismatic Hexagonalism Pattern No Background

Source GDJ

Part of Bayeux Tapestry 2 #2451
 Noise  CC 0

From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.

Source Firkin

Background pattern 215 (colour 2) #2370
 Blue  CC 0

A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.

Source Firkin

Prismatic Polka Dots Mark II No Background@2X #531
 Noise  CC 0

Prismatic Polka Dots Mark II No Background

Source GDJ

Prismatic Groovy Concentric Background 3 #457
 Noise  CC 0

Prismatic Groovy Concentric Background 3

Source GDJ

Textured Red Brown Plastic #878
 Wood  CC BY-SA 3.0

Textured Red Brown Plastic, Free Background Pattern. Although there's already enough plastic in our lives, let's bring it to the web too.)

Source V. Hartikainen

Decorative divider 271 #1923
 Dark  CC 0

Remixed from a drawing in 'Incidents on a Journey through Nubia to Darfoor', F. Ensor, 1891.

Source Firkin

Prismatic Groovy Concentric Background 3@2X #458
 Noise  CC 0

Prismatic Groovy Concentric Background 3

Source GDJ