Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
This one is quite simple in design, it consists of vertical stripes layered on top of a seamless texture.
Source V. Hartikainen
With a name like this, it has to be hot. Diagonal lines in light shades.
Source Isaac
A version without colours blended together to give a different look.
Source Firkin
An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Super dark, crisp and detailed. And a Kill Bill reference.
Source Badhon Ebrahim
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A light gray background pattern with seamless fabric-like texture and almost unnoticeable stripes.
Source V. Hartikainen
A free grid paper background pattern for using on web sites.
Source V. Hartikainen
From a drawing in 'Bond Slaves. The story of a struggle.', Isabella Varley, 1893.
Source Firkin
The image depicts a seamless pattern made using a bird's face.
Source Yamachem