Background pattern green #1947
 Green  CC 0

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

Source Firkin

 More Textures
Stucco #294
 Wall  CC BY-SA 3.0

A nice and simple gray stucco material. Great on its own, or as a base for a new pattern.

Source Bartosz Kaszubowski

Fire diamond #2488
 Diamond  CC 0

U.S.-based National Fire Protection Association standard fire diamond for flagging risks posed by hazardous materials. The red diamond has a number 0-4 depending on flammability. The blue diamond has a number 0-4 depending on health hazard. The yellow has a number 0-4 depending on reactivity. the white square has a special notice, e.g OX for oxidizer.

Source Firkin

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

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

Source Struck Axiom

Triangular Psychosis 2 #234
 Noise  CC 0

A colorful triangular background, variation 2.

Source GDJ

Background pattern 215 #2371
 Brown  CC 0

A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.

Source Firkin

Light Brown Wallpaper With Vertical Stripes #905
 Stripes  CC BY-SA 3.0

This seamless light brown background texture resembles a wallpaper with vertical stripes. One way to use it is as a tiled background on web sites.

Source V. Hartikainen

Fake Brick@2X #359
 Dark  CC BY-SA 3.0

Black, simple, elegant, and useful.

Source Marat

Hibiscus Flowers Seamless Background #229
 Fabric  CC 0

PDP

Source GDJ