Like the name suggests, this background image consists of a pattern of dark bricks. It may be an option for you, if you are looking for something that looks like a brick wall for use as a background on web pages. It's not a masterpiece, but looks pretty nice when is tiled.
Source V. Hartikainen
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
Might not be super subtle, but quite original in its form.
Source Alex Smith
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
Number 2 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A seamless striped fabric-like texture colored in a dark reddish brown color.
Source V. Hartikainen
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Luxurious looking pattern (for a T-shirt maybe?) with a hint of green.
Source Simon Meek
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso