The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Prismatic Rounded Squares Grid 3 No Background
Source GDJ
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Bumps, highlight and shadows – all good things.
Source Badhon Ebrahim
Kaleidoscope Prismatic Abstract No Background
Source GDJ
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
Colour version of the original pattern inspired by the front cover of 'Old and New Paris', Henry Edwards, 1894.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Prismatic Geometric Pattern Background
Source GDJ
Abstract Tiled Background Extended 12
Source GDJ
This ons is quite old school looking. Retro, even. I like it.
Source Arno Declercq
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Here I have tried to create something that would look like maple wood. Not sure how well it's turned out, but at least it looks like wood.
Source V. Hartikainen