Triangles@2X #128
 Dark  CC BY-SA 3.0

Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.

Source Ivan Ginev

 More Textures
Prismatic Dots Background 8 #515
 Noise  CC 0

Prismatic Dots Background 8

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

Sakura Blossoms Background #389
 Noise  CC 0

Sakura Blossoms Background

Source GDJ

Retro Squares Background #414
 Noise  CC 0

Retro Squares Background

Source GDJ

Diamond pattern (colour 7) #2274
 Red  CC 0

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

Source Firkin

Inflicted #117
 Grid  CC BY-SA 3.0

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

Source Hugo Loning

Prismatic Groovy Concentric Background@2X #450
 Noise  CC 0

Prismatic Groovy Concentric Background

Source GDJ

Grunge Wall@2X #82
 Wall  CC BY-SA 3.0

Light gray grunge wall with a nice texture overlay.

Source Adam Anlauf

Background pattern 7 #227
 Noise  CC 0

Pattern that came out of playing with the 'slinky' plug-in for Paint.net

Source Firkin

Background pattern 252 (colour 4) #2159
 Light  CC 0

Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

Seamless Prismatic Geometric Pattern With Background #264
 Dark  CC 0

Seamless Prismatic Geometric Pattern With Background

Source GDJ

Graphene pattern 2 #2234
 Dark  CC 0

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

Source Firkin

Decorative divider 293 #1752
 Dark  CC 0

From a drawing in 'An Old Maid's Love. A Dutch tale told in English', Maarten Maartens, 1891.

Source Firkin