Axiom Pattern #330
 Grid  CC BY-SA 3.0

Not even 1kb, but very stylish. Gray thin lines.

Source Struck Axiom

 More Textures
Geometric pattern #2004
 Grid  CC 0

A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i

Source Firkin

Zig Zag@2X #329
 Dark  CC BY-SA 3.0

So tiny, just 7 by 7 pixels – but still so sexy. Ah yes.

Source Dmitriy Prodchenko

Batthern #324
 Grid  CC BY-SA 3.0

Sometimes simple really is what you need, and this could fit you well.

Source Factorio.us Collective

Fabric 1@2X #10
 Light  CC BY-SA 3.0

Semi-light fabric pattern made out of random pixels in shades of gray.

Source Atle Mo

Silver Scales #189
 Light  CC BY-SA 3.0

Turn your site into a dragon with this great scale pattern.

Source Alex Parker

Decorative divider 254 #2040
 Dark  CC 0

Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857

Source Firkin

Prismatic Curved Diamond Pattern 6 No Background@2X #546
 Dark  CC 0

Prismatic Curved Diamond Pattern 6 No Background

Source GDJ

Small Crackle Bright #352
 Light  CC BY-SA 3.0

Light gray pattern with an almost wall tile-like appearance.

Source Markus Tinner

Double Lined #51
 Stripes  CC BY-SA 3.0

Horizontal and vertical lines on a light gray background.

Source Adam Anlauf