A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Remixed from an image on Pixabay uploaded by Prawny
Source Firkin
CC0 remixed from a drawing. Walter Crane, 1914, Firkin.
Source SliverKnight
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
Here's a new paper-like background for free use on personal and commercial projects (this applies to all background patterns here).
Source V. Hartikainen
A seamless pattern made from the gold Penrose triangle by GDJ and the two remixes
Source Firkin
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
The image depicts a seamless pattern of a tortoise in tortoiseshell (hexagon).
Source Yamachem
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
Prismatic Polka Dots Mark II No Background
Source GDJ
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
An abstract web texture of a polished blue stone (or does it look more like ice).
Source V. Hartikainen
A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin