People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Same as the black version, but now in shades of gray. Very subtle and fine grained.
Source Atle Mo
A version without colours blended together to give a different look.
Source Firkin
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Did anyone say The Hoff? This pattern is in no way related to Baywatch.
Source Josh Green
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless pattern formed from cross 4. To get the original tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Wild Oliva or Oliva Wilde? Darker than the others, sort of a medium dark pattern.
Source Badhon Ebrahim
The name is totally random, but hey, it sounds good.
Source Atle Mo
A seamless texture of black leather. I think it will look best when used in headers, footers or sidebars.
Source V. Hartikainen
Prismatic Snowflakes Pattern No Background
Source GDJ
Tile-able Dark Brown Wood Background. Feel free to use it as a background image in your designs or somewhere on the web. By the way, the color seems to be close to Coffee Brown.
Source V. Hartikainen
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green