Retro Squares Background 4@2X #419
 Dark  CC 0

Retro Squares Background 4

Source GDJ

 More Textures
Prismatic Polka Dots Mark II No Background@2X #531
 Noise  CC 0

Prismatic Polka Dots Mark II No Background

Source GDJ

Background pattern 225 (colour 4) #2324
 Green  CC 0

Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.

Source Firkin

"Gold Buttons", Pale Yellow BG Pattern #1215
 Yellow  CC BY-SA 3.0

This yellow background consists of a pattern of glossy gold buttons arranged in polka dot style on a seamless texture. Here's a pale yellow background pattern. Feel free to use it for your needs!

Source V. Hartikainen

Prismatic Groovy Concentric Background 5 #465
 Dark  CC 0

Prismatic Groovy Concentric Background 5

Source GDJ

Prismatic Polka Dots 3 No Background@2X #529
 Noise  CC 0

Prismatic Polka Dots 3 No Background

Source GDJ

Graphy #350
 Grid  CC BY-SA 3.0

Looks like a technical drawing board: small squares forming a nice grid.

Source We Are Pixel8

Retina Dust #915
 Light  CC BY-SA 3.0

First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.

Source Atle Mo

Vintage pattern #1961
 Grid  CC 0

Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.

Source Firkin

Background pattern 315 (colour 3) #1843
 Green  CC 0

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

Source Firkin