Inflicted #117
 Grid  CC BY-SA 3.0

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

Source Hugo Loning

 More Textures
Dark Stripes #39
 Dark  CC BY-SA 3.0

Very dark pattern with some noise and 45-degree lines.

Source Stefan Aleksić

Concrete Wall 2 #79
 Wall  CC BY-SA 3.0

A light gray wall or floor (you decide) of concrete.

Source Atle Mo

Prismatic Geometric Tessellation Pattern 4 No Background #557
 Noise  CC 0

Prismatic Geometric Tessellation Pattern 4 No Background

Source GDJ

Subtle Striped Brown Background Pattern #940
 Stripes  CC BY-SA 3.0

Here's a brown background pattern with subtle stripes. I hope you'll like the color. If not, feel free to change it using an image editor, if you know how of course. Personally, I'm using GIMP to create these backgrounds.

Source V. Hartikainen

Tactile Noise@2X #6
 Dark  CC BY-SA 3.0

A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.

Source Atle Mo

"Dark Brick Wall", Background Pattern #1024
 Stone  CC BY-SA 3.0

Like the name suggests, this background image consists of a pattern of dark bricks. It may be an option for you, if you are looking for something that looks like a brick wall for use as a background on web pages. It's not a masterpiece, but looks pretty nice when is tiled.

Source V. Hartikainen

Background pattern 254 (colour) #2143
 Colorful  CC 0

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

Source Firkin

Decorative divider 293 #1752
 Dark  CC 0

From a drawing in 'An Old Maid's Love. A Dutch tale told in English', Maarten Maartens, 1891.

Source Firkin

Prismatic Abstract Geometric Background 2 No Black #445
 Noise  CC 0

Prismatic Abstract Geometric Background 2 No Black

Source GDJ

Floral design 91 #1814
 Dark  CC 0

From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.

Source Firkin

Prismatic Pointers Background #388
 Noise  CC 0

Prismatic Pointers Background

Source GDJ

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