Dark Blue Gray Wallpaper Texture #901
 Stripes  CC BY-SA 3.0

This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!

Source V. Hartikainen

 More Textures
Black Scales@2X #192
 Dark  CC BY-SA 3.0

Same as Silver Scales, but in black. Turn your site into a dragon with this great scale pattern.

Source Alex Parker

Vintage pattern #1958
 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 105 #563
 Dark  CC 0

A seamless pattern formed from background pattern 102

Source Firkin

Diamond pattern (colour 4) #2282
 Blue  CC 0

From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

Rough Cloth #312
 Fabric  CC BY-SA 3.0

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

Source Bartosz Kaszubowski

Floral background 5 #2404
 Fabric  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

Squares@2X #303
 Dark  CC BY-SA 3.0

Dark, square, clean and tidy. What more can you ask for?

Source Jaromír Kavan

Prismatic Groovy Concentric Background 4 No Black #463
 Noise  CC 0

Prismatic Groovy Concentric Background 4 No Black

Source GDJ

Inflicted@2X #118
 Grid  CC BY-SA 3.0

Dark squares with some virus-looking dots in the grid.

Source Hugo Loning

Retro Squares Background 8 #398
 Noise  CC 0

Retro Squares Background 8

Source GDJ