Seamless Core Pattern 4 #168
 Dark  CC 0

Seamless Core Pattern 4

Source GDJ

 More Textures
Background pattern 2 #221
 Noise  CC 0

A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.

Source Firkin

Checkered Light Emboss #280
 Grid  CC BY-SA 3.0

Sort of like the Photoshop transparent background, but better!

Source Alex Parker

Lined Paper@2X #363
 Stripes  CC BY-SA 3.0

The classic notebook paper with horizontal stripes.

Source Are Sundnes

Retro Circles Background 5 No Black@2X #427
 Noise  CC 0

Retro Circles Background 5 No Black

Source GDJ

Abstract Ellipses Background #275
 Dark  CC 0

Abstract Ellipses Background

Source GDJ

Background pattern 18 #202
 Dark  CC 0

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

Source Firkin

crissXcross #111
 Dark  CC BY-SA 3.0

Dark pattern with some nice diagonal stitched lines crossing over.

Source Ashton

Fish Pattern Background #233
 Noise  CC 0

From PDP.

Source GDJ

Fabric pattern 2 (colour 6) #2391
 Fabric  CC 0

Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin