Zero CC tileable grass texture, photographed and made by me. CC0
Source Sojan Janso
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This one is super crisp at 2X. Lined paper with some dust and scratches.
Source HQvectors
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
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
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
New paper pattern with a slightly organic feel to it, using some thin threads.
Source Atle Mo
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
Derived from a JPG that was uploaded to Pixabay by ractapopulous
Source Firkin
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
A seamless web texture of "green stone".
Source V. Hartikainen
A beautiful dark wood pattern, superbly tiled.
Source Omar Alvarado
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
A seamlessly tile-able grunge background image.
Source V. Hartikainen
Prismatic Hexagonalist Pattern No Background
Source GDJ
Pattern Background, Texture, Photoshop Structure style CC0 texture.
Source Darkmoon1968
This one is amazing, truly original. Go use it!
Source Viahorizon