From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless background of warped stripes on paper.
Source V. Hartikainen
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
This was formed by distorting an image of a background on Pixabay.
Source Firkin
More in the paper realm, this time with fibers.
Source Jorge Fuentes
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion
One can never have too few rice paper patterns, so here is one more.
Source Atle Mo
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
A seamless pattern of leopard skin. It should look nice as a background element on web pages.
Source V. Hartikainen
A free pink background pattern.
Source V. Hartikainen
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
Wasn't satisfied with the original's colouring. Too much component transfer and colormatrixes yet the results are lacking a bit. So this time it is a simple black to transparent fade, making it possible remixing easily once there will be other blending modes supported as well. Probably in inkscape 0.92.
Source Lazur URH
A seamless pattern of "sewn stripes" colored in light gray.
Source V. Hartikainen
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
There are many carbon patterns, but this one is tiny.
Source Designova
Prismatic Groovy Concentric Background 4
Source GDJ
A seamlessly tile-able grunge background image.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso