Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Prismatic Hypnotic Pattern No Background
Source GDJ
Fix and cc0 to get the tile this is based on.
Source SliverKnight
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
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. Version with black background.
Source Firkin
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
The image depicts a seamless pattern of pine tree leaves.
Source Yamachem
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Prismatic Triangular Background Design Mark II 5
Source GDJ
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Seamless Dark Grunge Texture. Here's a new grunge texture for use as a background.
Source V. Hartikainen
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin
A free seamless texture of reptile skin colored in a dark brown color. As always, you may use it as a repeated background image in your web design works, or for any other purposes.
Source V. Hartikainen
Number 4 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos