This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
A seamless background pattern of dark brown wood planks.
Source V. Hartikainen
Love me some light mesh on a Monday. Sharp.
Source Wilmotte Bastien
A seamless pattern recreated from an image on Pixabay. It is reminiscent of parquet flooring and is formed from a square tile, which can be recovered in Inkscape by selecting the ungrouped rectangle and using shift-alt-I together.
Source Firkin
Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo
Colored maple leaves scattered on a surface. This is tileable, so it can be used as a background or wallpaper.
Source Eady
Prismatic Abstract Geometric Background 5 No Black
Source GDJ
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
Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
If you need a green background for your blog/website, try this one. Remember that Green Striped Background is seamlessly tileable.
Source V. Hartikainen
Kaleidoscope Prismatic Abstract No Background
Source GDJ
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
The tile can be had by selecting the rectangle in Inkscape and using shift+alt+i. Remixed from a drawing in 'Flowers of Song', Frederick Weatherly, 1895.
Source Firkin
Zero CC tileable pine bark texture, photographed and made by me. CC0
Source Sojan Janso
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Abstract Tiled Background Extended 8
Source GDJ
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin