Checkered Light Emboss@2X #281
 Grid  CC BY-SA 3.0

Sort of like the Photoshop transparent background, but better!

Source Alex Parker

 More Textures
Background pattern 272 #2057
 Brown  CC 0

A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

Background pattern 268 #2066
 Dark  CC 0

Remixed from a drawing in 'Kulturgeschichte der Deutschen im Mittelalter' Franz von Loeher, 1891. The unit tile can be had by selecting the rectangle in Inkscape and using shift-alt-i

Source Firkin

Floral design 70 #2520
 Dark  CC 0

Traced from a drawing in 'Household Stories from the Collection of the Brothers Grimm', Wilhelm Carl Grimm , 1882.

Source Firkin

Retro Circles Background 4 No Black #422
 Dark  CC 0

Retro Circles Background 4 No Black

Source GDJ

Background pattern 115-seamless pattern #2514
 Blue  CC 0

This is the remix of "Background pattern 115" uploaded by "Firkin".Thanks.

Source Yamachem

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

Retro Squares Background #414
 Noise  CC 0

Retro Squares Background

Source GDJ

Prismatic Groovy Concentric Background 4@2X #462
 Noise  CC 0

Prismatic Groovy Concentric Background 4

Source GDJ

Silver Scales #189
 Light  CC BY-SA 3.0

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

Source Alex Parker

Retro Circles Background 8 No Black@2X #438
 Dark  CC 0

Retro Circles Background 8 No Black

Source GDJ

Fish Pattern Background #233
 Noise  CC 0

From PDP.

Source GDJ

Wood Background Pattern #882
 Wood  CC BY-SA 3.0

A seamless background pattern with a texture of wood planks. This wood background pattern has vertically arranged planks. You may try to rotate it 90°, to see how it will look like when the wood planks are arranged horizontally.

Source V. Hartikainen