Background pattern 306 (colour 3) #1880
 Colorful  CC 0

Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.

Source Firkin

 More Textures
WaveCut #75
 Light  CC BY-SA 3.0

If you like it a bit trippy, this wave pattern might be for you.

Source Ian Soper

60º lines #25
 Light  CC BY-SA 3.0

Never out of fashion and so much hotter than the 45º everyone knows, here is a sweet 60º line pattern.

Source Atle Mo

Prismatic Geometric Pattern Background #407
 Noise  CC 0

Prismatic Geometric Pattern Background

Source GDJ

Green Gobbler@2X #86
 Dark  CC BY-SA 3.0

Luxurious looking pattern (for a T-shirt maybe?) with a hint of green.

Source Simon Meek

Retro Circles Background 8@2X #436
 Dark  CC 0

Retro Circles Background 8

Source GDJ

Carbon Fiber v2@2X #106
 Carbon  CC BY-SA 3.0

One more updated pattern. Not really carbon fiber, but it’s the most popular pattern, so I’ll give you an extra choice.

Source Atle Mo

Brushed Alum #67
 Light  CC BY-SA 3.0

A light brushed aluminum pattern for your pleasure.

Source Tim Ward

Prismatic Dots Background 4@2X #508
 Noise  CC 0

Prismatic Dots Background 4

Source GDJ

Background pattern 238 #2229
 Red  CC 0

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

Source Firkin

Background pattern 308 (colour 3) #1870
 Colorful  CC 0

Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.

Source Firkin

Interlocking pattern 3 (colour 2) #2405
 Grid  CC 0

A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.

Source Firkin

Hexagonal pattern (colour) #2378
 Yellow  CC 0

A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.

Source Firkin