Background pattern 339 (colour) #1708
 Yellow  CC 0

The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

 More Textures
Prismatic Rounded Squares Grid 4 No Background #491
 Noise  CC 0

Prismatic Rounded Squares Grid 4 No Background

Source GDJ

Background pattern 207 #2466
 Yellow  CC 0

A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

"Polished Stone", Gray Background Pattern #1053
 Stone  CC BY-SA 3.0

A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).

Source V. Hartikainen

fishnet 01 #2475
 Grid  CC 0

The image depicts a seamless pattern of a fishnet with a plenty of fish.It may be a lucky charm for fishermen.

Source Yamachem

Smooth Wall #27
 Light  CC BY-SA 3.0

Some rectangles, a bit of dust and grunge, plus a hint of concrete.

Source Atle Mo

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

Tessellation 15 (colour 2) #2221
 Yellow  CC 0

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

Source Firkin

Merely Cubed #589
 Grid  CC BY-SA 3.0

Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.

Source Etienne Rallion

Prismatic Dots Background 3 #505
 Noise  CC 0

Prismatic Dots Background 3

Source GDJ

Background pattern 8 (black) #209
 Dark  CC 0

Black version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net

Source Firkin

White Paperboard #374
 Fabric  CC BY-SA 3.0

Could be paper, could be a Polaroid frame – up to you!

Source Chaos