Zodiac pattern (black background) #267
 Dark  CC 0

A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I. Version with black background.

Source Firkin

 More Textures
Triangular Psychosis 4 #236
 Noise  CC 0

A colorful triangular background, variation 4.

Source GDJ

samekomon-02 #2263
 Pink  CC 0

The image is a remix of "edo pattern-samekomon".I changed the color of dots from black to white and added BG in light-brown.

Source Yamachem

Random Binary Background #274
 Light  CC 0

Random Binary Background

Source GDJ

Colorful Floral Background 3@2X #484
 Dark  CC 0

Colorful Floral Background 3

Source GDJ

Seamless Core Pattern 5 #169
 Dark  CC 0

Seamless Core Pattern 5

Source GDJ

Seamless tile 4 #1812
 Red  CC 0

Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern

Source Firkin

Dark Stripes@2X #40
 Dark  CC BY-SA 3.0

Very dark pattern with some noise and 45-degree lines.

Source Stefan Aleksić

Pinstripe #35
 Light  CC BY-SA 3.0

Light gray pattern with a thin pinstripe.

Source Brandon

Micro Carbon@2X #8
 Carbon  CC BY-SA 3.0

Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.

Source Atle Mo

Washi #288
 Light  CC BY-SA 3.0

Washi (和紙?) is a type of paper made in Japan. Here’s the pattern for you!

Source Carolynne

Prismatic Groovy Concentric Background 3 No Black #459
 Noise  CC 0

Prismatic Groovy Concentric Background 3 No Black

Source GDJ

Background pattern 215 (colour 4) #2368
 Green  CC 0

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

Source Firkin

Parquet flooring pattern (colour 3) #2425
 Pink  CC 0

A seamless pattern recreated from an image on Pixabay. It is reminiscent of parquet flooring and is formed from a square tile, which can be recovered in Inkscape by selecting the ungrouped rectangle and using shift-alt-I together.

Source Firkin

Colourful background #2007
 Colorful  CC 0

Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic

Source Firkin