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

 More Textures
Diamond pattern (colour 9) #2269
 Fabric  CC 0

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

Source Firkin

Retro Circles Background 4 #420
 Dark  CC 0

Retro Circles Background 4

Source GDJ

Padded@2X #62
 Dark  CC BY-SA 3.0

A beautiful dark padded pattern, like an old classic sofa.

Source Chris Baldie

Gold Triangular Seamless Pattern No Background #272
 Light  CC 0

Gold Triangular Seamless Pattern No Background

Source GDJ

Background pattern 223 #2353
 Red  CC 0

Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.

Source Firkin

Checkered Light Emboss #280
 Grid  CC BY-SA 3.0

Sort of like the Photoshop transparent background, but better!

Source Alex Parker

White Sand@2X #20
 Light  CC BY-SA 3.0

Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.

Source Atle Mo

Light Blue Background Pattern #1161
 Grid  CC BY-SA 3.0

This light blue background pattern is quite pleasing to the eye, it consists of a tiny rough grid pattern, which is seamless by design. That's it, if you like the color, you can use this seamless pattern in a web design without making any further modifications to it.

Source V. Hartikainen

Prismatic Hypnotic Pattern No Background #571
 Noise  CC 0

Prismatic Hypnotic Pattern No Background

Source GDJ

Inflicted@2X #118
 Grid  CC BY-SA 3.0

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

Source Hugo Loning

Padded #61
 Dark  CC BY-SA 3.0

A beautiful dark padded pattern, like an old classic sofa.

Source Chris Baldie

Smooth Wall #27
 Light  CC BY-SA 3.0

Some rectangles, a bit of dust and grunge, plus a hint of concrete.

Source Atle Mo