Starting Diamond Shape #137
 Light  CC BY-SA 3.0

Simple blue and line to mix.

Source SliverKnight

 More Textures
Broken Noise #364
 Dark  CC BY-SA 3.0

Beautiful dark noise pattern with some dust and grunge.

Source Vincent Klaiber

Background pattern 215 (colour 4) #2368
 Green  CC 0

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

Source Firkin

Seamless Prismatic Geometric Pattern With Background #264
 Dark  CC 0

Seamless Prismatic Geometric Pattern With Background

Source GDJ

Batthern@2X #325
 Grid  CC BY-SA 3.0

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

Source Factorio.us Collective

Background pattern 214 (colour 2) #2376
 Red  CC 0

A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.

Source Firkin

Background pattern blue #1949
 Blue  CC 0

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

Source Firkin

Retro Circles Background 7@2X #432
 Unknow  CC 0

Retro Circles Background 7

Source GDJ

Prismatic Curved Diamond Pattern 2 No Background #538
 Diamond  CC 0

Prismatic Curved Diamond Pattern 2 No Background

Source GDJ

Background pattern 230 (colour 2) #2302
 Green  CC 0

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

Source Firkin

Triangular Psychosis 2 #234
 Noise  CC 0

A colorful triangular background, variation 2.

Source GDJ

Psychedelic Geometric Background No Black #382
 Noise  CC 0

Psychedelic Geometric Background No Black

Source GDJ

Fleurs-de-lys pattern 2 (colour) #2204
 Colorful  CC 0

Colour version of the original pattern inspired by the front cover of 'Old and New Paris', Henry Edwards, 1894.

Source Firkin

Background pattern 252 (colour 3) #2160
 Green  CC 0

Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

Dark Denim #372
 Dark  CC BY-SA 3.0

Thin lines, noise and texture creates this crisp dark denim pattern.

Source Marco Slooten

Prismatic Hypnotic Pattern 2 No Background@2X #574
 Noise  CC 0

Prismatic Hypnotic Pattern 2 No Background

Source GDJ

Rice Paper #338
 Paper  CC BY-SA 3.0

Scanned some rice paper and tiled it up for you. Enjoy.

Source Atle Mo

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

Bright Squares #87
 Light  CC BY-SA 3.0

It’s okay to be square! A nice light gray pattern with random squares.

Source Waseem Dahman