More Textures
Geometric pattern #2005
 Grid  CC 0

A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i

Source Firkin

Prismatic Dots Background 5 #509
 Noise  CC 0

Prismatic Dots Background 5

Source GDJ

WaveCut #75
 Light  CC BY-SA 3.0

If you like it a bit trippy, this wave pattern might be for you.

Source Ian Soper

Seamless Prismatic Pythagorean Line Art Pattern No Background@2X #570
 Light  CC 0

Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).

Source GDJ

Cardboard #278
 Paper  CC BY-SA 3.0

A good starting point for a cardboard pattern. This would work well in a variety of colors.

Source Atle Mo

Prismatic Abstract Geometric Background 2 No Black #445
 Noise  CC 0

Prismatic Abstract Geometric Background 2 No Black

Source GDJ

Stucco #294
 Wall  CC BY-SA 3.0

A nice and simple gray stucco material. Great on its own, or as a base for a new pattern.

Source Bartosz Kaszubowski

Background pattern 19 (black) #203
 Dark  CC 0

A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.

Source Firkin