Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
Zero CC tileable ground (#2) cracked, crackled texture, made by me. CC0
Source Sojan Janso
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
From a drawing in 'Kingsdene', Maria Fetherstonehaugh, 1878.
Source Firkin
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 a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Could be paper, could be a Polaroid frame – up to you!
Source Chaos
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
Produced using the clouds, flames and glass blocks plug-ins in Paint.net and the resulting .PNG vectorised with Vector Magic.
Source Firkin
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
Utilising a bird from s-light and some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Scanned some rice paper and tiled it up for you. Enjoy.
Source Atle Mo
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Formed by distorting an image on Pixabay that was uploaded by gustavorezende. To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Snowflakes Pattern 2 No Background
Source GDJ