Background pattern pink #1948
 Pink  CC 0

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

Source Firkin

 More Textures
Background pattern 21 #205
 Light  CC 0

A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.

Source Firkin

Prismatic Curved Diamond Pattern 5 No Background #543
 Diamond  CC 0

Prismatic Curved Diamond Pattern 5 No Background

Source GDJ

Retro Squares Background 5 #395
 Dark  CC 0

Retro Squares Background 5

Source GDJ

Old Mathematics #43
 Stripes  CC BY-SA 3.0

This one takes you back to math class. Classic mathematic board underlay.

Source Josh Green

Psychedelic Geometric Background No Black #382
 Noise  CC 0

Psychedelic Geometric Background No Black

Source GDJ

Diamond pattern (colour 3) #2283
 Green  CC 0

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

Source Firkin

Concrete Wall 2@2X #80
 Wall  CC BY-SA 3.0

A light gray wall or floor (you decide) of concrete.

Source Atle Mo

Background pattern 248 (colour) #2180
 Yellow  CC 0

To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

Foggy Birds #579
 Light  CC BY-SA 3.0

Hey, you never know when you’ll need a bird pattern, right?

Source Pete Fecteau