Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
Inspired by this, I came up with this pattern. Madness!
Source Atle Mo
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Clover with background for St. Patrick's Day. Add to a card with a doily, ribbon, a leprechaun or other embellishments.
Source BAJ
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
A seamless pattern formed from a tile made from page ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
Clean and crisp lines all over the place. Wrap it up with this one.
Source Dax Kieran
Formed by distorting an image on Pixabay that was uploaded by gustavorezende. To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Floral patterns will never go out of style, so enjoy this one.
Source Lasma
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
Black & white version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
A free black metallic background pattern. Here's a new pattern I made that looks metallic.
Source V. Hartikainen
An alternative colour scheme to the original seamless pattern.
Source Firkin
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
Prismatic Rounded Squares Grid 3 No Background
Source GDJ