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
Rough Cloth #312
 Fabric  CC BY-SA 3.0

More tactile goodness. This time in the form of some rough cloth.

Source Bartosz Kaszubowski

Vintage pattern #1959
 Grid  CC 0

Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.

Source Firkin

Vintage Elegant Floral Background #257
 Fabric  CC 0

PDP

Source GDJ

Decorative divider 198 #2437
 Dark  CC 0

From a drawing in 'Codogno e il suo territorio nella cronaca e nella storia'', Gio and Giarella Cairo, 1897.

Source Firkin

Vintage tile background (colour 3) #2246
 Green  CC 0

A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.

Source Firkin

Prismatic Groovy Concentric Background 3@2X #458
 Noise  CC 0

Prismatic Groovy Concentric Background 3

Source GDJ

Black Paper #55
 Dark  CC BY-SA 3.0

Black paper texture, based on two different images.

Source Atle Mo
Based from Design Kindle

Background pattern 230 (colour 3) #2303
 Green  CC 0

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

Source Firkin