Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A light gray fabric pattern with faded vertical stripes.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
A background tile for web with abstract repeating texture of dark "stone wall".
Source V. Hartikainen
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Super dark, crisp and detailed. And a Kill Bill reference.
Source Badhon Ebrahim
This was formed by distorting an image of a background on Pixabay.
Source Firkin
The name is totally random, but hey, it sounds good.
Source Atle Mo
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
Nasty or not, it’s a nice pattern that tiles. Like they all do.
Source Badhon Ebrahim
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i
Source Firkin
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
Element of beach pattern with background.
Source Rones
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers