Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
A seamlessly tile-able grunge background image.
Source V. Hartikainen
Continuing the geometric trend, here is one more.
Source Mike Warner
Prismatic Geometric Pattern Background No Black
Source GDJ
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
Abstract Tiled Background Extended 6
Source GDJ
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
If you need a green background for your blog/website, try this one. Remember that Green Striped Background is seamlessly tileable.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
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
A light background pattern with diagonal stripes. Here's a simple light striped background for you.
Source V. Hartikainen
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin