Starting Diamond Shape #137
 Light  CC BY-SA 3.0

Simple blue and line to mix.

Source SliverKnight

 More Textures
Checkered Light Emboss #280
 Grid  CC BY-SA 3.0

Sort of like the Photoshop transparent background, but better!

Source Alex Parker

Noise Pattern With Subtle Cross Lines@2X #180
 Grid  CC BY-SA 3.0

More bright luxury. This is a bit larger than fancy deboss, and with a bit more noise.

Source Viszt Péter

Prismatic 3D Isometric Tessellation Pattern 6 #148
 Dark  CC 0

Prismatic 3D Isometric Tessellation Pattern 6

Source GDJ

Colorful Geometric Pattern Background #231
 Noise  CC 0

PDP

Source GDJ

Pool Table #175
 Wall  CC BY-SA 3.0

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

Source Caveman

“Transparent” Background Pattern #493
 Light  CC 0

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

Source AdamStanislav