Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
A free seamless background texture of "timber wall" (colored in dark brown).
Source V. Hartikainen
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
Dark blue concrete wall with some small dust spots.
Source Atle Mo
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
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
Remixed from an image on Pixabay, the original having been uploaded by darkmoon1968.
Source Firkin
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
All good things come in threes, so I give you the third in my little concrete wall series.
Source Atle Mo
The original enhanced with some gradients.
Source Firkin
Prismatic Abstract Background Design
Source GDJ
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo