Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A repeating background of beige (or is it more vanilla yellow) textured stripes. One more background with stripes.
Source V. Hartikainen
Colorful Floral Background 3 No Black
Source GDJ
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
Inspired by a design found in 'Konstantinápolyi emlékeim', Miklos Chriszto, 1893.
Source Firkin
Prismatic Floral Background No Black
Source GDJ
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
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Geometric Pattern Background 2 No Black
Source GDJ