Checkered Light Emboss #280
 Grid  CC BY-SA 3.0

Sort of like the Photoshop transparent background, but better!

Source Alex Parker

 More Textures
Background pattern 203 (colour 2) #2485
 Green  CC 0

A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

Background pattern #2000
 Dark  CC 0

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

Source Firkin

Background pattern 5 #224
 Noise  CC 0

A pattern drawn in Paint.net and vectorized in Inkscape.

Source Firkin

Paper 1 #15
 Paper  CC BY-SA 3.0

A slightly grainy paper pattern with small horizontal and vertical strokes.

Source Atle Mo

Seamless tile 4 #1812
 Red  CC 0

Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern

Source Firkin

Prismatic Dots Background 5@2X #510
 Noise  CC 0

Prismatic Dots Background 5

Source GDJ

Retro Circles Background 8@2X #436
 Dark  CC 0

Retro Circles Background 8

Source GDJ

Background pattern 314 (colour 2) #1838
 Green  CC 0

The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

Orange Gingham Checkered Background #258
 Stripes  CC 0

From PDP.

Source GDJ

Background pattern 232 #2297
 Dark  CC 0

Heavily remixed from a drawing in 'Barbara Leybourne; a story of eighty years ago', Sarah Hamer, 1889.

Source Firkin

Vintage pattern #1960
 Grid  CC 0

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

Source Firkin

Background pattern 339 #1709
 Dark  CC 0

The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

Background pattern 223 (colour 3) #2351
 Green  CC 0

Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.

Source Firkin