Prismatic Groovy Concentric Background 5@2X #466
 Dark  CC 0

Prismatic Groovy Concentric Background 5

Source GDJ

 More Textures
Graphy@2X #351
 Grid  CC BY-SA 3.0

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

Source We Are Pixel8

Prismatic Polka Dots Mark II 3 No Background #534
 Noise  CC 0

Prismatic Polka Dots Mark II 3 No Background

Source GDJ

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 238 (colour 3) #2227
 Blue  CC 0

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

Source Firkin

Always Grey@2X #54
 Dark  CC BY-SA 3.0

Crossing lines with a subtle emboss effect on a dark background.

Source Stefan Aleksić

Prismatic Curved Diamond Pattern 4 No Background@2X #542
 Diamond  CC 0

Prismatic Curved Diamond Pattern 4 No Background

Source GDJ