From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
I love these crisp, tiny, super subtle patterns.
Source Badhon Ebrahim
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
Background pattern made in "Grunge-Like" style. Available in both SVG and JPG formats. Edit to your needs then click the download button.
Source V. Hartikainen
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
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
The image depicts a seamless pattern of a tortoise in tortoiseshell (hexagon).
Source Yamachem
A seamless textured paper for backgrounds. Colored in pale orange hues.
Source V. Hartikainen