Background pattern 214 (colour 6) #2372
 Colorful  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

 More Textures
White carbon #11
 Carbon  CC BY-SA 3.0

Same as the black version, but now in shades of gray. Very subtle and fine grained.

Source Atle Mo

Black Mamba #57
 Dark  CC BY-SA 3.0

The name alone is awesome, but so is this sweet dark pattern.

Source Federica Pelzel

Prismatic Hypnotic Pattern 2 No Background@2X #574
 Noise  CC 0

Prismatic Hypnotic Pattern 2 No Background

Source GDJ

Prismatic Groovy Concentric Background 3 #457
 Noise  CC 0

Prismatic Groovy Concentric Background 3

Source GDJ

Background pattern 215 #2371
 Brown  CC 0

A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.

Source Firkin

Floral design 100 (version 2, colour) #1772
 Green  CC 0

From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.

Source Firkin

Prismatic Geometric Tessellation Pattern 3 No Background #555
 Noise  CC 0

Prismatic Geometric Tessellation Pattern 3 No Background

Source GDJ

Cincinnati tablet 2 #2146
 Dark  CC 0

Remixed from a drawing in 'Prehistoric Man: researches into the origin of civilisation in the old and the new world', Daniel Wilson, 1876.

Source Firkin

Background pattern 259 (colour 6) #2097
 Blue  CC 0

Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin