This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Detailed but still subtle and quite original. Lovely gray shades.
Source Kim Ruddock
Here's an yet another background for websites, with a seamless texture of wood planks this time.
Source V. Hartikainen
Vertical lines with a bumpy, yet crisp, feel to it.
Source Raasa
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
A seamless pattern based on a tile that can be achieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A free pink background pattern.
Source V. Hartikainen
A pale olive green background with a seamless texture.
Source V. Hartikainen
Run a restaurant blog? Here you go. Done.
Source Andrijana Jarnjak
A comeback for you: the popular Escheresque, now in black.
Source Patten
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein