I guess this is inspired by the city of Ravenna in Italy and its stone walls.
Source Sentel
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
Here's an yet another background for websites, with a seamless texture of wood planks this time.
Source V. Hartikainen
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
Tiny little flowers growing on your screen. Nice, huh?
Source Themes Tube
Continuing the geometric trend, here is one more.
Source Mike Warner
Subtle scratches on a light gray background.
Source Andrey Ovcharov
Prismatic Rounded Squares Grid 3 No Background
Source GDJ
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
From a drawing in 'Friend or Fortune? The story of a strange year', Robert Overton, 1897.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Abstract Line Art Pattern Background
Source GDJ
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The tile this fill pattern is based on can be had by using shift+alt+i on the rectangle.
Source Firkin
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
A comeback for you: the popular Escheresque, now in black.
Source Patten
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
A dark gray, sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
A version without colours blended together to give a different look.
Source Firkin