Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Small dots with minor circles spread across to form a nice mosaic.
Source John Burks
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
A light gray fabric pattern with faded vertical stripes.
Source V. Hartikainen
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
A seamless pattern formed from a modified version of rwwgub's tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
A version without colours blended together to give a different look.
Source Firkin
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
Prismatic Hypnotic Pattern 2 No Background
Source GDJ
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
The image depicts a seamless pattern of pine tree leaves.
Source Yamachem