Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
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 background pattern 102
Source Firkin
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Hey, you never know when you’ll need a bird pattern, right?
Source Pete Fecteau
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
This was formed by distorting an image of a background on Pixabay.
Source Firkin
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Clover with background for St. Patrick's Day. Add to a card with a doily, ribbon, a leprechaun or other embellishments.
Source BAJ
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
Inspired by this, I came up with this pattern. Madness!
Source Atle Mo
Just like your old suit, all striped and smooth.
Source Alex Berkowitz
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Prismatic Abstract Geometric Background 5
Source GDJ