A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a design in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Prismatic Polka Dots Mark II 2 No Background
Source GDJ
Another fairly simple design drawn in Paint.net and vectorized in Inkscape.
Source Firkin
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
Awesome name, great pattern. Who does not love space?
Source Nick Batchelor
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Prismatic Groovy Concentric Background 3 No Black
Source GDJ