Triangular Psychosis 4 #236
 Noise  CC 0

A colorful triangular background, variation 4.

Source GDJ

 More Textures
Vintage tile background (colour 3) #2246
 Green  CC 0

A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.

Source Firkin

Pool Table #175
 Wall  CC BY-SA 3.0

This makes me wanna shoot some pool! Sweet green pool table pattern.

Source Caveman

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

Inflicted #117
 Grid  CC BY-SA 3.0

Dark squares with some virus-looking dots in the grid.

Source Hugo Loning

Decorative divider 288 #1820
 Dark  CC 0

From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.

Source Firkin

Abstract Arbitrary Geometric Background #497
 Noise  CC 0

Abstract Arbitrary Geometric Background derived from an image on Pixabay.

Source GDJ

Background pattern green #2027
 Green  CC 0

Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

My Little Plaid@2X #333
 Light  CC BY-SA 3.0

Repeating squares overlapping.

Source Pete Fecteau

Colorful Geometric Pattern Background #231
 Noise  CC 0

PDP

Source GDJ

“Transparent” Background Pattern@2X #494
 Light  CC 0

An emulated “transparent” background pattern, like that of all kinds of computer graphics software.

Source AdamStanislav

Background pattern 105 #563
 Dark  CC 0

A seamless pattern formed from background pattern 102

Source Firkin

Background pattern 258 #2135
 Dark  CC 0

Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.

Source Firkin

Green Dust & Scratches@2X #108
 Wall  CC BY-SA 3.0

Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.

Source Atle Mo

Seamless Wood Pattern #889
 Wood  CC BY-SA 3.0

A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.

Source V. Hartikainen