Light Aluminum #304
 Wall  CC BY-SA 3.0

Used correctly, this could be nice. Used in a bad way, all hell will break loose.

Source Atle Mo

 More Textures
Background2@2X #477
 Wall  CC 0

rug texture background

Source Jilllio

Small Crosses@2X #116
 Stripes  CC BY-SA 3.0

Sharp pixel pattern looking like some sort of fabric.

Source Dmitry

Background pattern 19 (black) #203
 Dark  CC 0

A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.

Source Firkin

Prismatic Polka Dots Mark II No Background #530
 Noise  CC 0

Prismatic Polka Dots Mark II No Background

Source GDJ

Strawberry seamless pattern #208
 Noise  CC 0

This is the remix of "Strawberry Pattern Background" uploaded by "GDJ". Thanks. I realigned strawberries so as to get seamless and changed the BG color.

Source Yamachem

Sakura Blossoms Background #389
 Noise  CC 0

Sakura Blossoms Background

Source GDJ

Geometric pattern #2003
 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

Abstract Tiled Background Extended 11 #522
 Noise  CC 0

Abstract Tiled Background Extended 11

Source GDJ

Transparent Square Tiles #298
 Grid  CC BY-SA 3.0

The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.

Source Nathan Spady

Axiom Pattern@2X #331
 Grid  CC BY-SA 3.0

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

Source Struck Axiom