Hibiscus Flowers Seamless Background #229
 Fabric  CC 0

PDP

Source GDJ

 More Textures
Diamond pattern (colour 5) #2281
 Red  CC 0

From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

Transparent Square Tiles@2X #299
 Grid  CC BY-SA 3.0

The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.

Source Nathan Spady

Old Mathematics #43
 Stripes  CC BY-SA 3.0

This one takes you back to math class. Classic mathematic board underlay.

Source Josh Green

Background pattern 214 (colour 2) #2376
 Red  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

Prismatic Abstract Geometric Background 4 No Black@2X@2X #444
 Dark  CC 0

Prismatic Abstract Geometric Background 4

Source GDJ

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

Background pattern 207 #2466
 Yellow  CC 0

A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

Axiom Pattern@2X #331
 Grid  CC BY-SA 3.0

Not even 1kb, but very stylish. Gray thin lines.

Source Struck Axiom

Fabric pattern (colour 6) #2397
 Fabric  CC 0

Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

Prismatic Abstract Geometric Background 4 No Black #441
 Dark  CC 0

Prismatic Abstract Geometric Background 4 No Black

Source GDJ

Ribbon pattern 2 (version 2, colour 4) #2036
 Colorful  CC 0

The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin