Background pattern 41 #262
 Fabric  CC 0

A seamless pattern the starting point for which was a 'light rays' rendering in Paint.net.

Source Firkin

 More Textures
Washi #288
 Light  CC BY-SA 3.0

Washi (和紙?) is a type of paper made in Japan. Here’s the pattern for you!

Source Carolynne

Cross Stripes@2X #48
 Dark  CC BY-SA 3.0

Nice and simple crossed lines in dark gray tones.

Source Stefan Aleksić

Paper 1 #15
 Paper  CC BY-SA 3.0

A slightly grainy paper pattern with small horizontal and vertical strokes.

Source Atle Mo

Prismatic Rounded Squares Grid 3 No Background@2X #490
 Noise  CC 0

Prismatic Rounded Squares Grid 3 No Background

Source GDJ

Tessellation 15 (colour) #2222
 Blue  CC 0

The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.

Source Firkin

Soft Kill@2X #319
 Dark  CC BY-SA 3.0

Pattern #100! A black classic knit-looking pattern.

Source Factorio.us Collective

Background pattern 235 #2255
 Yellow  CC 0

To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

Background pattern 214 (colour 4) #2373
 Yellow  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

Starring@2X #586
 Dark  CC BY-SA 3.0

If you need stars, this is the one to get.

Source Agus Riyadi

Background pattern 104@2X #562
 Dark  CC 0

Background pattern 104

Source Firkin

My Little Plaid #332
 Light  CC BY-SA 3.0

Repeating squares overlapping.

Source Pete Fecteau

Background pattern 6 #226
 Noise  CC 0

A pattern derived from part of a fractal rendering in Paint.net.

Source Firkin