"Polished Stone", Gray Background Pattern #1053
 Stone  CC BY-SA 3.0

A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).

Source V. Hartikainen

 More Textures
Decorative divider 217 #2233
 Dark  CC 0

Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.

Source Firkin

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

Prismatic Dots Background 5

Source GDJ

Background pattern 10 #216
 Noise  CC 0

A pattern drawn in Paint.net and vectorized in Vector Magic.

Source Firkin

Prismatic Geometric Tessellation Pattern 3 No Background@2X #556
 Noise  CC 0

Prismatic Geometric Tessellation Pattern 3 No Background

Source GDJ

Tessellation 16 (colour 6) #2210
 Colorful  CC 0

The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i

Source Firkin

Always Grey #53
 Dark  CC BY-SA 3.0

Crossing lines with a subtle emboss effect on a dark background.

Source Stefan Aleksić

Glass block pattern #2477
 Brown  CC 0

Produced using the clouds, flames and glass blocks plug-ins in Paint.net and the resulting .PNG vectorised with Vector Magic.

Source Firkin

Gun Metal #360
 Dark  CC BY-SA 3.0

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

Source Nikolay Boltachev

Background pattern green #1953
 Green  CC 0

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

Source Firkin