This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
This is a seamless pattern which is derived from a flower petal image.
Source Yamachem
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
Turn your site into a dragon with this great scale pattern.
Source Alex Parker
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
This background pattern contains worn out colorful stripes as a texture.
Source V. Hartikainen
A seamlessly tile-able grunge background image.
Source V. Hartikainen
This background pattern looks like bamboo to me. Feel free to download it for your website (for your blog perhaps?).
Source V. Hartikainen
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Use shift+alt+i on the selected rectangle in Inkscape to get the tile this is based on
Source Firkin
This seamless pattern consists of a blue grid on a yellow background.
Source V. Hartikainen
A comeback for you: the popular Escheresque, now in black.
Source Patten
High detail stone wall with minor cracks and specks.
Source Projecteightyfive
A seamless green background texture. The image is distributed under a Creative Commons License (like all of the images here).
Source V. Hartikainen
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Fix and cc0 to get the tile this is based on.
Source SliverKnight
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
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
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A seamless pattern formed from a tile made from page ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin