Background pattern 309 (colour 2) #1865
 Blue  CC 0

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

Source Firkin

 More Textures
Diagmonds@2X #337
 Dark  CC BY-SA 3.0

Love the style on this one, very fresh. Diagonal diamond pattern. Get it?

Source INS

Colorful Geometric Pattern Background #231
 Noise  CC 0

PDP

Source GDJ

Background pattern 214 (colour 3) #2375
 Green  CC 0

A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.

Source Firkin

Graphene pattern 1 #2235
 Dark  CC 0

Different from the original in being a simple tile stored as a pattern definition, rather than numerous repeated objects. Hence easy and quick to give this pattern to objects of different shapes. To get the tile in Inkscape, select the rectangle and use shift+alt+i.

Source Firkin

"Dark Metal Plate", Web Background #1084
 Metal  CC BY-SA 3.0

A dark metal plate with an embossed grid pattern and a bit of rust. Here's a dark metal plate texture for use as a tiled background on web pages.

Source V. Hartikainen

Seamless Prismatic Geometric Pattern With Background #264
 Dark  CC 0

Seamless Prismatic Geometric Pattern With Background

Source GDJ

Abstract Arbitrary Geometric Background@2X #498
 Noise  CC 0

Abstract Arbitrary Geometric Background derived from an image on Pixabay.

Source GDJ

"Green Rhombuses", Seamless Background Pattern #1336
 Green  CC BY-SA 3.0

A free green background pattern with a pattern of rhombuses on a seamless texture. Feel free to use it as a tiled background image on your web site.

Source V. Hartikainen