A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A seamless background of warped stripes on paper.
Source V. Hartikainen
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
Dark pattern with some nice diagonal stitched lines crossing over.
Source Ashton
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
Prismatic Triangular Background Design Mark II 5
Source GDJ
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton
A pale yellow background pattern with vertical stripes. The stripes are partially faded. I think this background image turned out pretty well, especially those faded stripes.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
A nice one indeed, but I have a feeling we have it already? If you spot a copy, let me know on Twitter.
Source Graphiste
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
A seamless green background texture. The image is distributed under a Creative Commons License (like all of the images here).
Source V. Hartikainen
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin