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
From a drawing in 'Jardyne's Wife', Charles Wills, 1891.
Source Firkin
Prismatic Snowflakes Pattern No Background
Source GDJ
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
A textured blue background pattern with vertical stripes.
Source V. Hartikainen
From a drawing in 'Real Sailor-Songs', John Ashton, 1891.
Source Firkin
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova
A brown seamless wood texture in a form of stripe pattern. The result has turned out pretty well, in my opinion.
Source V. Hartikainen
An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
Prismatic Polyskelion Pattern No Background
Source GDJ
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
Used a cherry by doctormo to make this seamless pattern
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A pale olive green background with a seamless texture.
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
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin