Tile available in Inkscape using shift-alt-i on the selected rectangle
Source Firkin
A background pattern with a look of rough fabric.
Source V. Hartikainen
Prismatic Groovy Concentric Background 4
Source GDJ
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
The image depicts the Japanese Edo pattern called "seigaiha" or "青海波" meaning "blue -sea- wave".I hope it's suitable for the summer season.
Source Yamachem
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
You know you love wood patterns, so here’s one more.
Source Richard Tabor
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
From a drawing in 'Real Sailor-Songs', John Ashton, 1891.
Source Firkin
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen