Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.
Source Firkin
A repeating background of thick textured paper. Actually, it turned out to look like something between a paper and fabric.
Source V. Hartikainen
Colourful background achieved with gradient fills.
Source Firkin
Prismatic Hexagonalist Pattern No Background
Source GDJ
This one is amazing, truly original. Go use it!
Source Viahorizon
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
Based on an image that was uploaded to Pixabay by devanath
Source Firkin
Prismatic Hexagonalism Pattern No Background
Source GDJ
A beautiful dark padded pattern, like an old classic sofa.
Source Chris Baldie
Black version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
A floral background formed from numerous clones of flower 117.
Source Firkin
From a drawing in 'Az Osztrák-Magyar Monarchia irásban és képben', 1885.
Source Firkin
This one is amazing, truly original. Go use it!
Source Viahorizon
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
Prismatic Abstract Line Art Pattern Background
Source GDJ
A seamless pale yellow paper background with a pattern of animal tracks.
Source V. Hartikainen
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin