Green Fibers@2X #92
 Dark  CC BY-SA 3.0

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

Source Matteo Di Capua

 More Textures
Background pattern 272 #2057
 Brown  CC 0

A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

Background pattern 277 #2029
 Dark  CC 0

A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.

Source Firkin

Abstract Tiled Background Extended 8 #519
 Noise  CC 0

Abstract Tiled Background Extended 8

Source GDJ

Prismatic Curved Diamond Pattern 3 No Background@2X #540
 Diamond  CC 0

Prismatic Curved Diamond Pattern 3 No Background

Source GDJ

Groovepaper@2X #578
 Paper  CC BY-SA 3.0

With a name like this, it has to be hot. Diagonal lines in light shades.

Source Isaac

Bright Squares #87
 Light  CC BY-SA 3.0

It’s okay to be square! A nice light gray pattern with random squares.

Source Waseem Dahman

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

Ribbon pattern 2 (version 2) #2039
 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

Ribbon pattern 2 (version 2, colour 2) #2038
 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

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