Wood@2X #50
 Wood  CC BY-SA 3.0

Dark wooden pattern, given the subtle treatment. based on texture from Cloaks. https://cloaks.deviantart.com

Source Atle Mo

 More Textures
Inflicted@2X #118
 Grid  CC BY-SA 3.0

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

Source Hugo Loning

Background pattern 225 (colour 5) #2323
 Blue  CC 0

Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.

Source Firkin

Mirrored Squares #123
 Dark  CC BY-SA 3.0

Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.

Source Atle Mo

Diamond pattern 2 (colour 5) #2264
 Blue  CC 0

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

Source Firkin

Background pattern 26 (black) #199
 Dark  CC 0

Pattern formed from simple shapes. Black version.

Source Firkin

Leather 1 #13
 Light  CC BY-SA 3.0

A leather pattern with a hint of yellow.

Source Atle Mo