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 based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
A seamless texture of a rough concrete surface.
Source V. Hartikainen
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
This one is amazing, truly original. Go use it!
Source Viahorizon
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
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 SVG vector and JPG backgrounds with faded diagonal stripes. The colors are editable.
Source V. Hartikainen
Prismatic Groovy Concentric Background
Source GDJ
These dots are already worn for you, so you don’t have to.
Source Matt McDaniel
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Groovy Concentric Background 4
Source GDJ
One more brick pattern. A bit more depth to this one.
Source Benjamin Ward
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
From a drawing in 'Royal Ramsgate', James Simson, 1897.
Source Firkin
Zero CC tileable hard cover green book, scanned and made by me. CC0
Source Sojan Janso
Remixed from a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
A repeating background of beige paper with vintage look. Repeats to infinity, as usual.
Source V. Hartikainen