Background pattern 227 (colour 2) #2313
 Blue  CC 0

A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.

Source Firkin

 More Textures
Inflicted@2X #118
 Grid  CC BY-SA 3.0

Dark squares with some virus-looking dots in the grid.

Source Hugo Loning

Background pattern 308 (colour 2) #1871
 Green  CC 0

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

Source Firkin

Floral design 71 #2429
 Dark  CC 0

From a drawing in 'From Snowdon to the Sea. Striking stories of North and South Wales', Marie Trevelyan, 1895.

Source Firkin

Fabric (Plaid) #591
 Fabric  CC BY-SA 3.0

You know you can’t get enough of these linen-fabric-y patterns.

Source James Basoo

Prismatic Geometric Tessellation Pattern No Background@2X #552
 Noise  CC 0

Prismatic Geometric Tessellation Pattern No Background

Source GDJ

Prismatic Dots Background 6 #511
 Dark  CC 0

Prismatic Dots Background 6

Source GDJ

Background pattern 308 (colour 3) #1870
 Colorful  CC 0

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

Source Firkin

Background pattern purple #1998
 Colorful  CC 0

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

Source Firkin

Wine Cork #33
 Light  CC BY-SA 3.0

Wine cork texture based off a scanned corkboard.

Source Atle Mo

Dark Denim@2X #373
 Dark  CC BY-SA 3.0

Thin lines, noise and texture creates this crisp dark denim pattern.

Source Marco Slooten

Carbon Fiber v2@2X #106
 Carbon  CC BY-SA 3.0

One more updated pattern. Not really carbon fiber, but it’s the most popular pattern, so I’ll give you an extra choice.

Source Atle Mo