Seamless Colorful Floral Pattern Background #256
 Fabric  CC 0

PDP

Source GDJ

 More Textures
Seamless Core Pattern 2 #166
 Dark  CC 0

Seamless Core Pattern 2

Source GDJ

Colourful bricks pattern (no background) #265
 Noise  CC 0

Original minus the background

Source Firkin

Background pattern 8 (greyscale) #210
 Dark  CC 0

Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net

Source Firkin

edo pattern-samekomon #2271
 Dark  CC 0

The image depicts an edo-era pattern called "same-komon" or "鮫小紋"which looks like a shark skin.The "same" in Japanese means shark in English.

Source Yamachem

Prismatic Groovy Concentric Background 2 #453
 Noise  CC 0

Prismatic Groovy Concentric Background 2

Source GDJ

Fire diamond #2488
 Diamond  CC 0

U.S.-based National Fire Protection Association standard fire diamond for flagging risks posed by hazardous materials. The red diamond has a number 0-4 depending on flammability. The blue diamond has a number 0-4 depending on health hazard. The yellow has a number 0-4 depending on reactivity. the white square has a special notice, e.g OX for oxidizer.

Source Firkin

Abstract Arbitrary Geometric Background #497
 Noise  CC 0

Abstract Arbitrary Geometric Background derived from an image on Pixabay.

Source GDJ

Green Fibers #91
 Dark  CC BY-SA 3.0

The green fibers pattern will work very well in grayscale as well.

Source Matteo Di Capua

Background pattern 302 #1894
 Red  CC 0

The tile this fill pattern is based on can be had by using shift+alt+i on the rectangle.

Source Firkin

Background pattern 227 (colour 5) #2310
 Colorful  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

Dark Denim #29
 Dark  CC BY-SA 3.0

A dark denim looking pattern. 145×145 pixels.

Source Atle Mo

Real Carbon Fiber #286
 Carbon  CC BY-SA 3.0

Carbon fiber is never out of fashion, so here is one more style for you.

Source Alfred Lee