Sometimes you just need the simplest thing.
Source Fabricio
Original minus the background
Source Firkin
Prismatic Curved Diamond Pattern 4 No Background
Source GDJ
Non-seamless pattern drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
A seamless pattern formed from background pattern 102
Source Firkin
White handmade paper pattern with small bumps.
Source Marquis
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
From drawing in 'Musings in Maoriland', Thomas Bracken, 1890.
Source Firkin
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
Number 4 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
To get the repeating unit, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
A free web background image with a seamless concrete-like texture and an Indian-red color.
Source V. Hartikainen
Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A web texture of brown canvas. Will look great, when used in dark web designs.
Source V. Hartikainen
A seamless background pattern with a texture of wood planks. This wood background pattern has vertically arranged planks. You may try to rotate it 90°, to see how it will look like when the wood planks are arranged horizontally.
Source V. Hartikainen
Derived from a drawing in 'Historiske Afhandlinger', Adolf Jorgensen, 1898.
Source Firkin
I have no idea how to describe this one, but it’s light and delicate.
Source JBasoo
Actually remixed from a pattern on Pixabay. But then noticed a very similar one on Openclipart.org uploaded by btj51q2.
Source Firkin
Black And White Floral Pattern Background Inverse
Source GDJ
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Prismatic Groovy Concentric Background 5
Source GDJ