Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Seamless pattern inspired by a drawing on Pixabay. To get the tile this is formed from, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
Remixed from a PNG that was uploaded to Pixabay by gingertea
Source Firkin
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A nice and simple gray stucco material. Great on its own, or as a base for a new pattern.
Source Bartosz Kaszubowski
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
Bright Multicolored Floral Background by Karen Arnold from PDP.
Source GDJ
Tiny little fibers making a soft and sweet look.
Source Badhon Ebrahim
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin