A bit strange this one, but nice at the same time.
Source Diogo Silva
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Polka Dots Mark II No Background
Source GDJ
Square design drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
The edges of all the red objects line up either vertically or horizontally, but it doesn't appear so. Made from a square tile that can be got by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Prismatic Groovy Concentric Background
Source GDJ
A nice and simple white rotated tile pattern.
Source Another One
Have you wondered about how it feels to be buried alive? Here is the pattern for it.
Source Hendrik Lammers
Abstract Stars Geometric Pattern Prismatic No Background
Source GDJ
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
Remixed from a drawing in 'A Girl in Ten Thousand', Elizabeth Meade, 1896.
Source Firkin
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
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
More Japanese-inspired patterns, Gold Scales this time.
Source Josh Green
Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.
Source Firkin
Derived from an image that was uploaded to Pixabay by TheDigitalArtist
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
Imagine you zoomed in 1000X on some fabric. But then it turned out to be a skeleton!
Source Angelica
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Pattern that came out of playing with the 'slinky' plug-in for Paint.net
Source Firkin
Prismatic Groovy Concentric Background 3
Source GDJ
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley