More Textures
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

Seamless Core Pattern 3 #167
 Dark  CC 0

Seamless Core Pattern 3

Source GDJ

Subtle Freckles@2X #90
 Light  CC BY-SA 3.0

This is so subtle: We’re talking 1% opacity. Get your squint on!

Source Atle Mo

Diamonds Are Forever@2X #184
 Diamond  CC BY-SA 3.0

Sharp diamond pattern. A small 24x18px tile.

Source Tom Neal

Rubber Grip@2X #102
 Dark  CC BY-SA 3.0

A very slick dark rubber grip pattern, sort of like the grip on a camera.

Source Sinisha

Background pattern 259 (colour 4) #2131
 Green  CC 0

Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin