Colourful bricks pattern (no background) #265
 Noise  CC 0

Original minus the background

Source Firkin

 More Textures
Background pattern 215 #2371
 Brown  CC 0

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

Source Firkin

Dark Brick Wall #135
 Wall  CC BY-SA 3.0

Black brick wall pattern. Brick your site up!

Source Alex Parker

Checkered Pattern@2X #323
 Grid  CC BY-SA 3.0

Simple gray checkered lines, in light tones.

Source Radosław Rzepecki

Prismatic Hexagonalism Pattern No Background #391
 Light  CC 0

Prismatic Hexagonalism Pattern No Background

Source GDJ

Background pattern 328 (colour 6) #1796
 Red  CC 0

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

Source Firkin

Colourful background #2007
 Colorful  CC 0

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

Source Firkin

Diamond pattern (colour 5) #2281
 Red  CC 0

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

Source Firkin

Prismatic Rounded Squares Grid 4 No Background@2X #492
 Noise  CC 0

Prismatic Rounded Squares Grid 4 No Background

Source GDJ