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

 More Textures
Prismatic Geometric Tessellation Pattern 3 No Background@2X #556
 Noise  CC 0

Prismatic Geometric Tessellation Pattern 3 No Background

Source GDJ

Seamless Cardboard Texture #1212
 Cardboard  CC BY-SA 3.0

A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.

Source V. Hartikainen

Prismatic Abstract Line Art Pattern Background 2 #567
 Dark  CC 0

Prismatic Abstract Line Art Pattern Background 2

Source GDJ

Maze-seamless pattern #2555
 Grid  CC 0

This is the remix of an Openclipart clipart called "Maze" uploaded by "any_ono_mous".Thanks.This is a seamless pattern of a maze.

Source Yamachem

Retro Squares Background 4@2X #419
 Dark  CC 0

Retro Squares Background 4

Source GDJ