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

 More Textures
Abstract Stars Geometric Pattern Prismatic No Background #384
 Noise  CC 0

Abstract Stars Geometric Pattern Prismatic No Background

Source GDJ

Prismatic Groovy Concentric Background 5 No Black #467
 Dark  CC 0

Prismatic Groovy Concentric Background 5 No Black

Source GDJ

Background pattern 270 #2061
 Dark  CC 0

A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

Woven@2X #291
 Dark  CC BY-SA 3.0

Can’t believe we don’t have this in the collection already! Slick woven pattern with crisp details.

Source Max Rudberg