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 306 (colour 4) #1877
 Colorful  CC 0

Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.

Source Firkin

Background pattern 274 #2041
 Dark  CC 0

Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.

Source Firkin

Polaroid@2X #188
 Wall  CC BY-SA 3.0

Smooth Polaroid pattern with a light blue tint.

Source Daniel Beaton

Prismatic Curved Diamond Pattern 4 No Background@2X #542
 Diamond  CC 0

Prismatic Curved Diamond Pattern 4 No Background

Source GDJ

Gun Metal #360
 Dark  CC BY-SA 3.0

With a name this awesome, how can I go wrong?

Source Nikolay Boltachev

Pool Table@2X #176
 Wall  CC BY-SA 3.0

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

Source Caveman

Fabric pattern (colour 2) #2401
 Fabric  CC 0

Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

Greek key pattern 5 #2294
 Dark  CC 0

Seamless pattern made from a tile that can be obtained in Inkscape by selecting the rectangle and using shift+alt+i.

Source Firkin

Decorative divider 289 #1819
 Dark  CC 0

From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.

Source Firkin

Broken Noise@2X #365
 Dark  CC BY-SA 3.0

Beautiful dark noise pattern with some dust and grunge.

Source Vincent Klaiber

Floral pattern 7 (colour 4) #2288
 Green  CC 0

Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.

Source Firkin