Retro Circles Background 4 #420
 Dark  CC 0

Retro Circles Background 4

Source GDJ

 More Textures
Floral Pattern Background 5 #219
 Noise  CC 0

PDP

Source GDJ

Background pattern 308 (colour 5) #1869
 Blue  CC 0

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

Source Firkin

Prismatic Hypnotic Pattern 2 No Background@2X #574
 Noise  CC 0

Prismatic Hypnotic Pattern 2 No Background

Source GDJ

seigaiha subtle color #2278
 Pink  CC 0

This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .

Source Yamachem

Carbon Fiber Big@2X #327
 Carbon  CC BY-SA 3.0

Bigger is better, right? So here you have some large carbon fiber.

Source Factorio.us Collective

Prismatic Groovy Concentric Background No Black@2X #452
 Noise  CC 0

Prismatic Groovy Concentric Background No Black

Source GDJ

Cardboard #278
 Paper  CC BY-SA 3.0

A good starting point for a cardboard pattern. This would work well in a variety of colors.

Source Atle Mo

Handmade Paper #37
 Paper  CC BY-SA 3.0

White handmade paper pattern with small bumps.

Source Marquis

“Transparent” Background Pattern #493
 Light  CC 0

An emulated “transparent” background pattern, like that of all kinds of computer graphics software.

Source AdamStanislav

Soft Wallpaper #95
 Wall  CC BY-SA 3.0

Coming in at 666x666px, this is an evil big pattern, but nice and soft at the same time.

Source Atle Mo

Seamless Core Pattern #165
 Dark  CC 0

Seamless Core Pattern

Source GDJ