Transparent Square Tiles@2X #299
 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

 More Textures
Background pattern 258 #2135
 Dark  CC 0

Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.

Source Firkin

Floral background 2@2X #430
 Wall  CC 0

Background formed from the original with an emboss effect

Source GDJ

Dark Stripes@2X #40
 Dark  CC BY-SA 3.0

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

Source Stefan Aleksić

Lined Paper #362
 Stripes  CC BY-SA 3.0

The classic notebook paper with horizontal stripes.

Source Are Sundnes

Wine Cork@2X #34
 Light  CC BY-SA 3.0

Wine cork texture based off a scanned corkboard.

Source Atle Mo

Background pattern 250 (colour 3) #2169
 Colorful  CC 0

To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

Zodiac pattern #2407
 Colorful  CC 0

A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i

Source Firkin

Colorful Geometric Pattern Background #231
 Noise  CC 0

PDP

Source GDJ