A seamless pattern drawn originally in Paint.net by distorting a slice of background pattern 116 and copying the resulting triangle numerous times.
Source Firkin
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.
Source Lazur URH
A seamless pattern of "sewn stripes" colored in light gray.
Source V. Hartikainen
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
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
A seamless pattern formed from a rectangular tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
From a drawing in 'Kingsdene', Maria Fetherstonehaugh, 1878.
Source Firkin
Floral patterns will never go out of style, so enjoy this one.
Source Lasma
I have no idea what J Boo means by this name, but hey – it’s hot.
Source j Boo
Zero CC bark from fur tree tileable texture, photographed and made by me. CC0
Source Sojan Janso
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
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
A seamless web texture with illustration of pale color stains on canvas.
Source V. Hartikainen