Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
A set of paper filters. The base texture is generated the same way, only the compositing mode is varied.
Source Lazur URH
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
A beautiful dark padded pattern, like an old classic sofa.
Source Chris Baldie
Remixed from a drawing in 'Some account of the Worshipful Company of Ironmongers', John Nicholl, 1866.
Source Firkin
A seamless pale yellow paper background with a pattern of animal tracks.
Source V. Hartikainen
Prismatic Abstract Geometric Background 5 No Black
Source GDJ
A free light orange brown wallpaper with vertical stripes designed for use as a tiled background on websites. An yet another background pattern with vertical stripes.
Source V. Hartikainen
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A seamless texture of worn out "cardboard".
Source V. Hartikainen
A new one called white wall, not by me this time.
Source Yuji Honzawa
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Tile available in Inkscape using shift-alt-i on the selected rectangle
Source Firkin
It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
This light background pattern has a texture of "frozen" surface with diagonal stripes. Here's an yet another addition to the collection of free website backgrounds.
Source V. Hartikainen
Background formed from the original with an emboss effect.
Source Firkin
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
Seamless Light Background Texture.
Source V. Hartikainen
The Grid. A digital frontier. I tried to picture clusters of information as they traveled through the computer.
Source Haris Šumić
The original has been presented as black on transparent and stored in the pattern definitions. To retrieve the unit tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
A pale olive green background with a seamless texture.
Source V. Hartikainen
Derived from a JPG that was uploaded to Pixabay by ractapopulous
Source Firkin