Dark Stripes #39
 Dark  CC BY-SA 3.0

Very dark pattern with some noise and 45-degree lines.

Source Stefan Aleksić

 More Textures
Medic Packaging Foil #376
 Light  CC BY-SA 3.0

8 by 8 pixels, and just what the title says.

Source pixilated

Lego background #2428
 Colorful  CC 0

Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.

Source Firkin

Paisley Background #495
 Light  CC 0

Paisley Background

Source GDJ

Decorative divider 274 #1922
 Dark  CC 0

Redrawn based on a drawing in 'По Сѣверо-Западу Россіи' Konstantin Sluchevsky, 1897.

Source Firkin

Transparent Square Tiles #298
 Grid  CC BY-SA 3.0

The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.

Source Nathan Spady