This is a hot one. Small, sharp and unique.
Source GraphicsWall
Here I have tried to create something that would look like maple wood. Not sure how well it's turned out, but at least it looks like wood.
Source V. Hartikainen
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Prismatic Rounded Squares Grid 3 No Background
Source GDJ
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
Prismatic Snowflakes Pattern No Background
Source GDJ
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
Prismatic Groovy Concentric Background No Black
Source GDJ
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
Alternative colour scheme. 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
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A large pattern with funky shapes and form. An original. Sort of origami-ish.
Source Luuk van Baars
A dark brown fabric-like background texture with seamless pattern of winding stripes.
Source V. Hartikainen
An abstract Background pattern of purple twisty patterns.
Source TikiGiki
The original enhanced with some gradients.
Source Firkin
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
The image depicts a seamless pattern of pine tree leaves.
Source Yamachem
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Seamless Prismatic Geometric Pattern With Background
Source GDJ