From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
Prismatic Geometric Pattern Background 2 No Black
Source GDJ
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Psychedelic Geometric Background No Black
Source GDJ
You know I’m a sucker for these. Well-crafted paper pattern.
Source Mihaela Hinayon
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
An abstract pale yellow paper-like background with stains colored in yellow and green.
Source V. Hartikainen
A seamless background pattern of dark brown wood planks.
Source V. Hartikainen
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Prismatic Groovy Concentric Background 4
Source GDJ
Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A pattern derived from part of a fractal rendering in Paint.net.
Source Firkin